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LETTERS TO THE EDITOR.
fWe do not hold ourselves responsible for the opinions of onr correspondents. The Editor respectfully requests that all communications fihould be drawn up as briefly as possible.]
*#* All communications should be addressed to the Editor of the English Mechanic, 81, Tavistock street, Covent Garden, W.C.
All Cheques and Post Office Orders to be made payable to J. Passsiore Edwards.
* I would have every one write what he know*, and as much As he knows, but no more; and that not in this only, but in all other subjects: For such a person may have some particular knowledge and experience of the nature of such a person or such a fountain, that as to other things, knows no more than what everybody does, and yet to keep a clutter with this little pittance of his, will undertake to write the whole body of physicks: a vice from whence great Inconveniences derive their original."—Montaigne's Essays,
 Sir,—I may perhaps be permitted, under the above heading, to notice a few queries of a somewhat heterogeneous character, which would otherwise involve two or three separate short letters.
ImprimU: If Mr. Gould's "Ingenious Friend," to whom he refers on p. 378, were to take his gun down to the equator he would find that he might fire it either due east or due west without making any difference whatever, either in the range or flight of the ball, the earth and gun, pro Hid vice, forming one system. On the other hand were he to fire it either north or south a theoretical deflection would undoubtedly take place.
I much fear that it is the telescope of the " Optical Bricklayer " (same page) which is in fanlt; albeit, according to his showing it is by no moans placed in a good situation for observing with. Still, imperfect discs to stars seem to indicate a defective figure to some extent in the speculum. With regard to Saturn he is of course very near the horizon, and unfavourably situated for observation; but your correspondent ought to see very considerably more detail than he appears to do with? and 5-16th inches of aperture. With your permission, sir, an engraving showing the precise aspect of the planet at present, in & perfect 4 Jin. achromatic, will Appear in these columns in the course of a week or two. This will enable the " Optical Bricklayer '* to see how far his mirror fails in definition of this particular object. I am, of course, assuming that the eyepiece my querist employs has no defect in it; but at the same time 1*20 is far too low a power to use upon Saturn, and, for the matter of that, upon a star either, with such an apertnre a- he has.
Your " Subscriber" (4220), p. 882, will require the following lenses for the construction of the eyepieces he proposes to make :—1st for his 50-power, eye-lens, *53in; field-lens, l*(tin. Secondly, for the power of 100, eye-lens, 27in ; field lens, -8iu; and, thirdly, for that of 150, eye-lens -18in; and field-lens '58in. The practical detail asked for will all be found on p. 270 of the 5th vol. of the Emglish Mechanic.
It might probably tend to obviate the difficulty under which M Gunel" (425b"), p. 883, labours, were the sentence which he quotes from Todhnnter, transposed thus:—" The ratio of the circumference of a circle to its diameter is invariably denoted by the symbol A-." If he will read the words in this order, and then reflect that as the circumference of a circle contains the the diameter ir (8*1415926) times, it must contain the radius 2ir times—and, quite obviously, that the semicircumference (180 or two right angles) must contain the radius half this number (.or it) times—he will, I think, see that the two statements to which he refers are perfectly in accordance with each other.
Since I wrote the letter which you honoured me by printing on p. 360, I have received my copy of the current number of the Royal Astronomical Society's ** Monthly Notices." I find that it contains animperfect ephomeris of Winnecke's comet down to the 5th of this month, on which day its right ascension is given as 2h. 15m. 42s., and its north declination 1- 50, Berlin mean midnight. It would thus be to the north of o (Mira) Ceti. It is travelling rapidly in a S.E. direction. But for the morning twilight it might be visible to the naked eye.
A in,.)•■■ of the reference you make to mo (in your 11 Answers to Correspondents ") in connection with the Astronomical Register I may say that I quite endorse what Mr. Proctor says, with regard to the value of its reports of the meetings of tho Royal Astronomical Society, which are certainly nnparalleled in any other serial; but that my chief complaint against it is the abominable dilatoriuess with which it is published. Of all things on the face of the earth, it is essential that an Ephemeris should appear in advance of the time to which it refers; but my "Register" never reaches me until the 3rd of the month, and has been ninch later. Considering the nature of its contents, this is quite indefensible, and naturally damages its already limited circulation. A Fellow Of The Royal Astronomical Society.
Errata.—On p. 369, coL 2, line 3 from the bottom, dele "but." In the next column on line 8, " It is" is printed for "He Is;" and on the 11th line, "lapsis " for "lapsus." Again on line 30,1 find " object " put where I wrote " effect." Turning to coL 2 of p. 870, the word
brass," on line 25, is converted Into " trap," and on lino 81, " polish " appears for " polisu«r."
[48J Sir,— In the article on starch (page 162, No. 267, Vol. XI.) there are two little mistakes, "Inulien" should be Inulin; eleven lines from the end a full stop is inserted, where a comma only ought to have been placed—after " fennel; " this said, I proceed with the article from where I left off. 1st. The otfice performed by starch in nature.—Starch is the usual form in which nutriment is stored up for the future wants of plants or their offspring; the reservoirs in wliieh this nutriment is stored are generally either the root, the seed, or, if perennial, frequently the stem. In tho seed, and in such productions as the potato, the store is laid up for the use of new individuals, in other cases for the future growth of the same individual. The starch grain appears to be uttached to the side of the cell in which it is contained, aud probably at the point or by the points called the hilum. It is difficult to distinguish the exact point of attachment, on account of the intervention of the cell wall; but by the difference of focus required to distinguish the two surfaces of the cell, it is easy to see whether a grain is contiguous to the floor or roof of the cell; if the attachment is by the hilum that point ought to be turned away from you when it is fixed to the floor, and towards you if fixed to the roof; as far as my observation goes this is always the case. If the grains were not attached, frequent movements might be expected to take place amongst them in the uninjured colls; but movement of the grains in these cells is the exception. The hilum of starch, like that of the seed, varies in appearance in the different kinds of starch; in the potato it appears as a point, generally more or less elevated above the surrounding surface. I have sometimes thought I could detect an appearance like a very small circle, the central portion, when viewed by transmitted light, not brighter than the surrounding. The hilum in wheat starch assumes various forms, such as a point, curved line.&c, and is at least generally even with the surrounding surface; in arrowroot it assumes frequently a fissured appearance, more or less depressed, the light being reflected from the sides. These instances may serve the present purpose. For the purpose of illustrating the formation and use of the starch grain, we cannot do better than follow the gTOWth of the potato. The cells of the potato germ contain starch grains from their first development; during the early growth of the germ these are carried outwards in their containing cells, and may be seen in a thin section of the sprout. They are the first of the store consumed, and the difference in size between them and the grains in the body of the potato soon becomes evident. The vessels of the germ are distributed in the substance of the potato, similarly to the fibres of roots. The starch is contained in cells, the walls of which admit only of the passage of liquids; therefore, before it can serve as nutriment to the plant, it must be brought into a liquid state. With the growth of the plant, the size anduumber of the gmiiH contained in these* diminishes until there are scarcely any left. The absorbable state is probably produced in a similar way to that in a germinnting barley grain; that is, by the action of a special substance. Bat while starch is being assimilated, the production of starch is still going on. On making a section of the year's shoot of many plants, a number of minute particles are observed in the colls, and floating in tho liquid on the slide, some of which turn blue under the action of iodine; in some, larger bodies are observed, whieh appear to the eye in all respects like starch grains, giving also the characteristic colonr with iodine. This is the case with the potatoplant. A number of grains, generally more or less oval in form, are found, chiefly in cells surrounding the central portion of the shoot. As starch must become liquid before it can be absorbed by the vessels of the plant, these grains must have been formed in the cells in which they are found. The potato has not grown long before it begins to provide for future wants. It sends out side shoots underground called pendulum*, the ends of which become enlarged, forming the potato. The sole function of the potato is to serve as a storehouse of nutrition for tho buds developed on its surface, from the size of a pea to its full size; it consists of a number of cells containing starch grains, which appear to increase by successive deposits of the substance which composes them. The second special store is laid up in the seed, to supply nourishment for the development of the embryo. The starch grains serving this purpose are, at least generally, smaller than those stored up in the root or stem. In many seeds a mass of cells exists surrounding the young plant analogous to the substance of the potato; in, others the nutriment is only stored up in the seed leaves, which become* detached when the plant is in a condition to procure sustenance from tho earth, after which the history of Its internal economy is similar to that of its parent. Light seems to be necessary for the production of starch; potato-plants deprived of their proper supply of light produce tubers whieh .ire deficient iu starch, or are what ore called watery—this is the result of reading, not my own observation. The green colouring-matter of leaves, called chlorophyll— for production of which light is indispensable—is sometimes produced in the samo cells with starch, and it has struck me that the form of the two kinds of groin seem to bear some relation to each other. The grains of chlorophyll seem to be attached to tho walls of their containing cells, and frequently to have a point on their surface. Their chemical properties are of course very different. In blanched leaves I have noticed the cells are not empty, though deficient in chlorophyll, the little grains, showing the blue colour with iodine, occupy the cells, and appeared to me just as numerous.
But, as tills subject has only just come under my notice, I must defer further expression of opinion on
it until more observations and experiments have been carried out. Of course, as the grains are frequently too small to observe the shape, with a magnifying power of between 400 and 500 diameters, particulars above alluded to refer to the larger grains. The mode in which starch appears to be formed seems to bear some analog^' to crystallization—the definite point of aggregation—the increase by deposition, of material on the outside—the cross shown under-, the action of polarized light, all seem to bear tlus out. The last point I will refer to is prevalence of starchy matter in the air. On examining water under tho microscope that has been exposed to the air for a short time, yon rarely fail to find bodies, appearing to the eye like starch grains, and, on adding iodine solution, these groins give the characteristic starch bine. These grains are so prevalent, that it is difficult to obtain water without them, at least I have fouud it so. In the World of Science for July 27, 18G7, there is an article headed "Experiments with the Microscope on the Effects of Prussic Acid on the Animal Economy," being a paper by T. Shearman Ralph, read before the Medical Society of Victoria, from which I will make a few quotations, leaving the readers to judge its bearing upon the subject in hand, not presuming to express any opinion myself. He says, "If the ordinary prussic acid of Scheele be examined under the microscope, under a power of 200 diameters, the acid, if pure, will present nothing worthy of remark; hut occasionally specimens will be met with, which contain Prussian blue, and also a number of starchylooking bodies, which actually turn purple with iodine
these changes will be found to take place in
it, if tho bottle is repeatedly opened and portions taken out ever so carefully." He goes on to say, "These remarkable changes appear to, me to be duo to t)u rencucd access of air, and minute particles of dust getting in, and to the possible electric state of the glass rod." He says if after "a period of many days the bottle be shaken, and a drop placed on a slide, and examined with a microscope, bright blue particles will be seen
with a number of starchy-looking bodies,
which polarize feebly and turn purple with iodine, like vegetable starch." "On taking a drop of prussic acid free froin such contamination and some organic matter be added these starchy bodies
will make their appearance. First of all a minute dot,
resembling an oil globule, will be seen, which
will be observed to increase in size, sometimes attaining to that of an ordinary starch groin and
then it will nssnme a thicker consistence, and solidify into a starch grain," &c. The prevalence of starch in the air would account for its presence in the liquid. The last part of the quotation I must leave. Lastly, is it safe to rely solely upon the property of turning violet under the action of iodine, as a test for the presence of starch? ,
Starch grains are considered frequently to form part of the contents of pollen grains; and certainly mauy of the particles forming the contents show the supposed characteristic colour with iodine. The pollen of the Ealla turns a deep purple—almost black—when touched with the iodine solution; the transparency and thinness of the skin allow the contents to be seen through; and yet I have never been able to detect starch in water iu which pollen grains have been heated, whatever quantity I used of the pollen.
PURIFICATION OF FEATHERS, HAIR, Etc.
 Sir,—The aphorism of the discovery of the circulation of the blood—" omue animal ex ovo"—is specially applicable to all tho cognate facts (practically educed) from our present knowledge of the impurities of bedding and the mode of remodying its pernicious and wasteful effects,—pernicious because the conditions of health depend upon the adoption of that remedy, and wasteful, inasmuch as all materials, even though "doctors disagree," are alike subject to the devourer moth, and tho parasite. That their causes have their spring in the nature of the material we cannot deny; but nevertheless, the neglect of certain rules—viz., tho submission of all material to the process under consideration—must inevitably eliminate and develop the ova in question. Horse-hair, so called, cannot where the markets are competitive be produced pure and simple —in other words, that of the buffalo, ox, bison, and pig, is proportionately intermixed. At the extremity the epidermis, and occasionally minute portions of cuticle, adhere. The curling does not destroy the tendency to generate ova. Wool and other material, from its naturally oily nature, is also subject to the ravages of neglected attention, alias moth, Ac. Feathers occasionally are subject to their attack, but in a much less degree, inasmuch as these must be prepared by some process before it is possible to use them. All tho inferior materials used by the moderns cannot but bo tho hot bed, so to say, of these destroyers, inasmuch as old carpets in which they have loig made their homo, old clothing—in a word, the mixed refuse— Ac., contribute their quota to multiply them. And now to speak of the more mystic causes—these will bo manifest upon unfolding facts. "If from the body's purity the mind derives a secret and sympathetic aid," the homes of the wealthier portion of the community should be subject to special vigilance in ascertaining the condition of all bedding, and cause them to be subject to a process capable of fulfilling all its intentions, and must be appreciable in an economical as well as sanitary aspect. It will, of course, he readily conceded the necessity of preserving the greatest immunity from all cutaneous and febrile maladies, but others of a more subtle nature demand equal attention. The process employed in manipulating is one simple and effective. 1st. Thoroughlv saturating with alkalies of a certain strength. 2nd. Submitting the materials to sulphur dioxide in combination with water of a certain specific gravity, so as not to destroy the material. 3rd. "Well steaming at a pressure of two atmospheres. 4th. Removing to rotator}* drying chambers, and finally to the dusting machine. By this process, feathers, hair, wool, &c., acquire a freedom from imparities, also elastic properties, and an intrinsic value not to be obtained by other means. R. F. G.
 Sir,—I Bend a rough sketch of the method for boring cylinders, which I think will serve to give "Amateur Turner" a slight idea of how they are fixed to the saddle of lathe, and likewise the sort of tool generally used to effect a true and Bmooth cut. The finrt thing to do is to plane off the valve facing on cylinder — that is in case the steam chest is not cast on. After planing the face, fix the cylinder on the saddle of lathe, as shown in the sketch, then firmly bolt the cylinder to the saddle, Bo a* to keep it from moving in any direction during the process of boring; this being done, fix the boring bar between the centres of lathe, taking care to have the boring bar sufficiently long enough to allow the cylinder to pass over the tool, or else the cylinder would come in contact with the back head. The saddle of lathe would be self-acting, so that when the saddle moved, the cylinder would move with it. The cutter would be firmly fixed on cutter bar, Bo that the cylinder would form the feed to the cutter. This is only one of the many ways used in boring cylinders. Turners have various ways for boring cylinders, hut in the case described, the bore of cylinder would be true to a nicety with the valve facing. But where the cylinder wil not allow of being Itolted to the saddle, pieces of planed iron are pnt under the valve facing to keep it np to the required height. Tho tool shown is one that will effect a regular and true cut. owing to the number of cutters fixed ou the edge of cnttcr boss. Some turners use more cutters than others for boring J in some cases there is only the bar, and one cutter fixed in a slot on the bar; but a true oat cannot be effected with this, for if the hole in cylinder shonld be cant a little out, there would be mare metal to cat one side than the oHier; the consequence would be that when the cutter came around to take a deep cut one side and a light one the other, it would spring the bar, or press tho cylinder over; whereas, in the other case, all the cutters would be cutting at one time, so that one or other of the cutters would always be in the deep cut, and keep the cutter bar, likewise the cylinder, from moving. In the course of a few publications, I will send a sketch showing how cylinder covers are turned on both sideTM, without any holes through them.
J. C. Molloky, Exeter.
into A and project beyond, as B. Fit about 2in. of it into A, so that, the dimensions of the square being 5 jiu. X 6jin. x Bin., there will be just Sin. projection of B outside of A ^all the measurements are outside). C is of exactly the same construction as A, and has in addition a front with a hole for the lens. With the above you obtain from 6in. to 9in. focus. C is fixed to the bottom hoard D. D has a groove or rather slit through the centre for the screw and nut E to work in, in order that the back A may slide in and out of C as far as you like, the screw and nut E tightening it when required. A works in a kind of shute formed by the pieces F F. Now in the sides of A and in the bottom there must be grooves for the focussing screen G of Fig. 1 and Fig. 2 to work in. At the bottom is a hole on one Bide of the slit (that E works in), for the triangle to be fixed to, if one is used. U a table tripod is used, no hole is required.
Fig. 2 is the dark slide or back. A is a shutter that runs in a light-tight groove. B is a hinged door, also light-tight. It is almost impossible to describe the making of Fig. 2. "Snatch Block" would do better to ask some photographer to let him sec one. It is the most difficult thing in the whole apparatus to make. The cost of them is from 15s. upwards, from a manufacturer. C in Fig. 2 is a loop of leather to open B with. G of Fig. 1 is only some finely ground French glass fixed in a frame. I must impress upon the mind of the maker the ubsolute necessity of having the gronnd glass exactly the distance from the lens that the prepared plate will be when in the back. Without that the whole is useless.
Fig. 3 is a table stand. A is a flat piece of wood attached to B, which is a rod that runs in a hole in the blocks C and D. Therhandle E keeps it from slipping, so that it can be placed at any required height.
I fear that my description is not very clear, but as clear as I can make it, it being a very difficult thing, unless the maker is used a little to joining.
Let us hope that any one trying it may succeed; and that the tools may he in good order, and the wood not warp, is the sincere wish of Mis.
ELECTRICITY. — REACTION OF CURRENTS. AIR-PUMP.
 Sir,—Without going particularly into the subject mooted by " R. P. S.,*' p. 375, for which I have not time at present, I may say that he is correct in his supposition, because it is well known that if several currents are acting on a magnet, it will take the direction which is the resnltant of the several actions. Of course not only the direction but the force of the current also must be considered, the position taken being due to the combined actions and calculable from that which each of the currents acting singly would produce, hence it is not possible to draw such a figure as he does without taking the relative farces of the currents into account and also the resistance offered bv the magnet itself.
I did not reply to " Induotoiium's" earlier questions on the air-pump because he expressly limited the replies t. the result of actual experiment on the tame subject, but as he now takes a different position I may be able to help him. If I am not mistaken he will find
is thus no space left in the barrel to hold air; the piston is drawn back the barrel and receiver are ii connection and come to equal pressure. The piston* as soon as it passes, closes the connection and compress** the air in the barrel, but does not depend for its expulsion on this compression rising beyond that of the outer air and lifting the valve; but even than it seems to me that no possible exactness can prevent a little air following the piston on its return. For my own part I like the Tate's pump best of any I have tried, as I find that it exhausts very closely and with much less labour than any of the ordinary pumps.
The battery described by Mr. Conisbee is the Call&u or Maynooth Battery which I have referred to, a.ud quite agree with Mr. Conisbee as to its demerits, for which its cheapness at first is a very poor compensation indeed; but the cell enquired for was the Calland, a French device, and from the description evidently on«* of the numerous modifications of the Daniel.
A CHEAP WATER BAROMETER.
 Sir,—Enclosed Ib drawing of cheap water barometer, which I have had at work for some month*, and it has not differed more than *05in. from a good mercurial barometer during that time.
R is a small glass retort.
T T, a glass tube, graduated into inches ai tenths.
V, a vessel containing mixture of alcohol and water coloured with aniline.
B B, a stout piece of cord, 8in. x loin., fastened to wall.
A A A, a circular card, revolving on an axis, svnd carrying with it the pointer, a.
d d d, :i circle inscribed on B B, and graduated in- ■ inches and tenths.
c e et a larger circle, graduated (after trial) into barometric inches, Ac.
Now fill V with mixture as above.
T T (which must be at least 20in. long) is now titi-: air-tight with wax, into the neck of R. When hard heat R gently over lamp to expand the air therein. and immediately plunge bottom of tube T T into liquid in V. The air cooling and contracting will drawup liquid to (say) Oin., when it ceases rising; observe thermometer (say) 5t" Fahr. Now by turning AAA around till pointer a coincides with* 6 on d d d, the barometer is indicated, and supposing it to stand at 80*5, set the same down on the outer circle, e c e.
The liquid may rise only to lin. Then temp. 64 brought round shows 2*J2. Again, temp. 58°, glas* 2in. — U0 barometer. Corsi'bia.
SUN SPOTS.  Sir,—I beg to forward a sketch of a remarkable sun-spot observed here on the 21st ult.t with an equatorial, by Cooke, of 4in. aperture, power 900. When first seen, on June 19th, it was nearly central, eye, 5'; station point, 12ft. Ex. 4, Fig. B, 1ft. to left of spectator draw a cube of 4ft. Ride.
Make point B 1ft. to left of line of direction; from B to A equal 4ft.. and as the cube is on the PL, describe a square which will be the real size, and from the angles, A, B, C, D, draw lines to the 0 V, and from B draw a line to the D Pl, which will cut off the length of the retiring side A E. Make E F parallel to A B, erect perpendiculars from these points, and the figure is complete, leaving the one to the right to the ingenuity of the stndent, it being the same size, but one side coming on the line of direction. Ex. 5, Fig. 0, is a pyramid of 2ft. side, its altitude being 7ft., the nearest side 2ft. to the right of spectator.
and formed the preceding spot of a large scattered group, which measured about 2' 02' in length. At 10 a.m. on the last mentioned date, an isolated mass of light, intensely bright and of a crescent shape, was remarked on a nucleus. This was carefully watched at intervals during the day; at noon it was no longer isolated, but formed a "bridge" connecting adjacent aides of the umbra. At 5 p.m. there were no traces of it, the penumbra having encroached upon the place which it occupied during the early part of the day.
On June 21st the spot appeared as represented in the accompanying drawing. The cyclonic type of the penumbra is here evident.
After the 21st nit., the group showed unmistakable Bigns of closing np ; on the 24th it disappeared at the limb.
An unusual feature in the spot, and indeed in most of the large spots observed during the present year, waB the uneven colonr of the nucleus, which was very far from being uniform, patches of every shade, from a comparatively light brown to an intense black, were remarked. On the 21st nit., less than half the area of the nuclens was black; the remainder was of various shades of brown interspersed with small black patches. It is noteworthy that on the 19th ult. the central portion of the nuclens was brown and the edeiet black, and there was no gradual shading off between the brown and the black, but a sudden transition from one tint to the other.
As the sun is jnst now an object of great interest to astronomical students, perhaps some of your nnmerons readers have noticed similar phenomena.
I have observed and drawn most of the large sunspots which have appeared during the past five or six years; but, until the present epoch of maximum solar
activity, have generally found the umbra* of large spots
much more uniformly black than they now are.
Is this peculiarity connected in any way with the
present comparative shallowness of the penunibrre as
remarked by Mr. Lockyer? Bedford, July C. Thob. G. Elger.
Assuming the reader to have some knowledge of practical geometry, we will begin.
Here we have two planes lying on the ground, one of them parallel to and touching the picture^line, 2ft. to the right, it being 2ft. square.
Set off A 2ft. to right, and B 2ft. more. Run off lines from both to the C V, to cut off on the retiring line B 0, 8 ft. from A. Run off to the P D2 to the right, and B C is the perspective length of A B; draw the line C D parallel to the P plane, and the figure is complete. On the left is another plane, 8 ft. square; but instead of being removed to one side, one edge, F G, is exactly in a line with the spectator. Set off F E Sft. on the PL. From E run np to the C V; take a line from F to the P Di to left. The intersection H is the point through which to draw the line to form the back edge of the square.
 Sir, — Perspective fa often divided in two parts—viz., parallel and angular—the former when a side is towards the spectator, the hitter when an angle is seen.
Parallel perspective is generally given first in lectures ou'the subject, so we will follow the rule and treat it first.
In a cube, or any other right-angled object, having one of its faces parallel to the P P, the sides will vanish to the C of V, as stated in the last, and by rule.
As things in perspective do not appear less till they are beyond the picture plane, all measurements taken on the ground line are true and geometrical. _ It mn-» be remembered that man has not an unlimited field of vision right and left, unless he moves his head. The angle of vision is limited to 60°, and a spectator looking along the line of direction towards the C of V can only see to the right and to the left above and below that line 80", or, in other words, SO' all round. Therefore, the line of direction is the axis of the cone of visnal rays—the eyes of the spectator being the apex and the circular" base being on the picture plane (see fig. 2), so that objects coming outside the circlo become distorted, and to Bee more we must stand farther back. It is not necessary to draw the base of the cone in every drawing, but it must be borne in mind.
Sufficient theory has been given for the present: we will begin with the practical part, under the conditions adopted by the Science and Art Department examinations, some of whose second grade papers I intend to introduce. Let the scale be 1-iu. to the foot, making the picture line and horizon line 5ft. apart, the station point being 12ft. from the centre of vision.
Let the stndent now reverse the planes, putting the large one to the right and the small one to the left under the same conditions.
Ex. 8, Fig. 4, is a series of horizontal planes—we will call them pavements ; that on the right begins 1ft.
to the right. Set off from A 1ft. to the points 1, 2, 3, 4, each being 1ft. apart; from them run off to the C V. From 1 run off to P D2. Now the intersection on line 2 is 1ft. within the picture; S is 2ft., and on line 4 is 8ft. Rule horizontal lines through tho intersections, and the pavement is complete. This is a very instructive exercise on horizontal planes. I leavo the other to the skill of the reader, they being the same size, the second lot being 4ft. behind the other. If the student cannot see this clearly, complete the first without regard to those behind, and from point 8 draw a line to the D P, which will cut off the required distance, and proceed as before. We will now leave tho plaues'aud commence with the solids. Scale, Jiu. = If t.
Ex. 6, Fig. 7, is a box of which the dimensions are given, the lid being open 1ft. Produce a similar one to l»ft, and remove it 1ft. within tho picture.— J. W. Bedford.
ELLIPTICAL GEARING.  Sir,—I send a drawing of a pair of elliptical wheels made as they ought to be, but never are. It is troublesome to set the teeth out, as each side of every tooth should be of the form that would suit a circular wheel of that particular radius ; also pricking the pit«h off the pitch line (represented by a dotted line), makes the teeth come a little thinner on the side of the wheels than round the ends, which does not signify, as the same teeth must come into gear with each other at every revolution, and so yon may set them out as thick or thin as you please. Also it is to be observed that if at one end of the wheel a tooth comes exactly on the centre line, as is the case in the drawing at A and B, then the number of teeth must be odd. If for any
reason an even number is required, then, at tho ends, the «i<i< of a tooth must come on the centre line, as is the case with the tooth at C, and the wheels must be put on the shafts heads and tails together. There is no objection to making the tops and bottoms of the teeth square if preferred, and there is no necessity for any contrivance for keeping them in gear, which ordinary elliptical wheels do require. Proved.—J. K. P.
UNEQUAL STEAM PRESSURE.  Sir,—With vour kind permission, I purpose replying to Mr. Wood, teriatim. on the above topic in Vol. X., No. 258, page 606, where I think he has treated us to a somewhat elaborate but erroneous lecture on unequal steam pressure, when contrasted with the general opinion entertained by the most eminent engiHivis of this llHh century; for they one, aud 1 may venture to say all, believe in equal steaming.
Mr. Wood, ut the outset of his last letter, Bays that we may have unequal steam pressure by having one valve right and the other too late, and the engine would be working right then to all appearance.
Now I have exainiuedjMr. Wood's theoretical diagrams, which I will now explain. No. 1 has got an average pressure of 171b. No. 2 has got an average pressure of nearly 131b., that is 41b. more on one side of the piston than the other, yet Mr. Wood has pronounced this engine us running right to all appearance.
After that we have diagrams No. 3 and No. 4, represented as being taken after the valves had been altered ■jiu. at the cross-head, and of course must be the improved ones. We have no account of any more work being added to the engine at this juncture, \vt the engine is actually taking Gib. more steam ou the piston at each half-stroke; whereas if he had obtained by the alteration a continuous and steady motion, ho would have required less, consequent on the fact tliat he had dispensed with the back-lash, or jars in the machinery, produced by unequal steaming.
If Mr. Wood cannot convey his thoughts to paper without the use of diagrams, it would bo much better if he would be more careful in tilling them up properly, or otherwise put the proper scale, to them. In No. 1 figure, at the beginning, we have gin. representing I4'51b. A little higher up the figure we have $iu. and 91b. marked. In No. 2, we have ut the beginning ^in. l-:J2nd and lo*51b. marked. If Mr. Wood can read this scale by measuring it, I must say he's an expert, as it is neither l-10th, 1-iiOth, 1-iJOth, l-40th, or l-60th Hcale; perhaps he knows whut it is. According to Mr. Wood's items, we have in No. 1 figure, at the commencement of the Btroke, the steam coming on very easy, a pressure of 14&lb; in No. 2 we have only 13$lb. (one lb. less) and l-10th of the piston's stroke late, which amounts to a severe shock at the extreme points of suspension. We will suppose this engine to have a fMun. stroke, divided by IU, which gives Gin. the distance the piston would have traversed down the cylinder before any steam could be admitted to support the piston's motion. In this case we have unequal steam pressure, amounting to 41b. more on an average nudemcath the piston than at the top side. We have the greatest prime mover applied at the proper time. On the other side we have the least prime mover, coupled with the evil of the pi&tou being moved down the cylinder 5in., it makiug a partial stop.at this point; therefore a portion of the lea.-»t prime mover has to be absorbed at this portion of the stroke in obtaining that regular speed and steady motion which has been lost by unequal steaming and unequal application of the ptime mover. Yet Mr. Wood has pronounced this engine to be running all right. I would ask Mr. Wood why he was called in to alter this engine if it was all right. The proprietors would not call any one in tc alter their engine unless their suspicions had been aroused unfavorable to its proper working. As Mr. Wood heema rather dull in apprehending the bad effects of unequal steaming and unequal application of the prime mover, and confounding the good by real assumption of the bad, I will just give another simple, but I hope it will be an effective, illustration of this gigantic power unequally applied, which Mr. Wood is now advocating. We will suppose half a dozen gentlemen to enter some engine-room when the engine is running. This shouldbe steady motion, which now present4 itself to their view, is nothing more nor less than effects produced by a current of alternate causes. If- the engineer, one amongst the six, can discover, by any instrument known, <>r by his own practical touches on the machinery, that those effects are unequal, he knows then that the alternate current of causes must be the same. When they nave discovered that the visible effects are unequal, Mich as irregular motion, and jars in the machinery of any kind, the least scientific amongst the six will come to the conclusion all at once that, as the visible effects are unequal, the alternate current of causes must be also. Scientific men never expect anything else as a rule, much le*s engineers. Again, when "Inquirer" put forth his query, the subject he sought, I believe, was equal 6tcaining. Mr. Wood perhaps, venturing outside his own avocation, tried to supply him with the requisite information to obtain this end. After this he comes in the corresponding field advocating and supporting with the greatest tenacity of purpose unequal steaming, and in such a manner as to astonish every engineer I am acquainted with. Yet under these unfavourable circumstances, an engine is said to be running all right. So according to Mr." Wood's version of the steam-engine, it will work right any way. He wants to know whether "Inquirer's" engine (high pressure) is doing three-fourth* of the work: if so, he must differ from me. There is no doubt of that: he will differ, and very much too, on the whole. I never said they were getting this amount of power through it, but simply used that rather high figure to convert him (Mr. Wood) to the practice of equal steaming and equal straining, which is quite as necessary to be attended to as the former. Mr. Wood says that I seem to have an idea that the steam ought to bo worked up in the high pressure engine cylinder. I have no such thought as that, and the lap I recommend would not work the steam up any more than what would remove the compression, and perhaps not that if they did not get an equal application of the prime mover (steam). Rut if the steam cannot be worked up effectually in the low pressure cylinder, it must be worked np in the higli pressure. Again, he state-; that "Inquirer's" high pressure cylinder should be 15in. diameter, and the steam kept on the piston ^ of its Btroke. The -pair combined,
low and high pressure, would then give out a eteadj" motive power. As the high pressure cylinder is to be loin., it will be about Hi nominal horse-power. We will suppose that we get 4 times its nominal horse-power from it, which is pretty fair rating for compound engines—i.e. 04horse-power indicated; steam being cut off at J of the stroke. Mr. Wood should have told "Inquirer" where he must cut the steam off in the low pressnre engine to obtain the same amount of equal force, us it-is just as necessary to know the latter as it is the former, if he must secure equal straining, and that steady motive power which he says would be given out. Again, he must bear in mind that if the engine* don't give out equal indicated horse-power, he cannot possibly get equal strains from the same unequal sources. In compound engines, the object of the engineers should be to divide the strains in the working materials in addition to working the steam np from a very high boiler pressure to the lowest one practicable in the low pressure <\JiuAr. Therefore, if the engine was properly constructed, and full of simplicity in the original design, they would get more practical results out of the steam (with the same sized engine) thau they would out of the single engine with the advantage of the strains being more equally diffused in the working materials; whereas in the single engine, or expanding the steam in one cylinder, the whole power, as it were, being concentrated at the extreme points of suspension, is sufficient to break it down in very many cases. We will just illustrate this case. Suppose we have got a pair of engines compounded, and we were getting five times their nominal power out of each engine; that would be ten times the nominal power for the single engine if you dispensed with one; Bo the engine we kept on working would have to be of very strong build indeed to sustain the severe strains at the extreme points of suspension; the other portion of the stroke it would be running nearly without strains. Again, he says the diagrams in No. 230, as stated before, are not so good to form judgment from as those in No. 242, inasmuch as the back pressure is not marked on them.
I answer, the indicator has not failed to delineate in this case the back pressure in the original figures any more than it has in the figures in No. 242, only the originals have been taken with a much stronger spring attached to the indicator piston, consequently they have a much less scale. If, when the indicator is fixed and the atmospheric line is made, then the form of the figure—the division between the atmospheric line and the lignre—is the back pressure in high pressure engines. If the indicator does not mark the back pressure, then the. operator simply takes the form of the figure and omits taking the atmospheric line. In that case the paper would be minus the back pressure, but the originals have got both line and figure. Again, I can't see what the back pressure has had to do with the information Mr. Wood has imparted to "Inquirer" previous to this controversy; for not one jot of information lias had any reference to that part of the figure which he deems so difficult to understand. He says that in my next (meaning this) instead of saying that "Inqnirer" must put Jtn. of lap on his valve, I Bhall perhaps say gin. or Jin. No; I shall not do that. What does he mean by this assertion? Does he mean because I have made a little mistake that I have falsified myself? I think if Mr. Wood will just reflect over this last assertion of his, he will discover that he has exceeded the bounds of jnstice and not done as he would like other correspondents to do unto him. Again, he says that if I had had an extensive practice with hips uud staffs, and the indicator, I should not tall them guess work.
And no it seems from this assertion that improper language would have been more congenial to Mr. Wood's feeling than proper, for in this case had I used the singular term (lap) instead of the plural (laps) he would not have attacked me on this point. Again, if he knew anything about engineering shop rudiments (which it is very evident he does not recognize), his feelings would have revolted at an assertion of this sort, inasmuch as staffs and lines of the most exquisite nature, both in the drawing office and in the workshop, have for this last century in particular formed the base of all the engineering processes of our greatest progressing engineers. Must this greatest perhaps of all sciences Ik* abolished at the instigation of one man, whose practice is so little in this direction that he has never been able to enjoy it—" no, nover."
Again, as far as guess work is concerned, I never said that the use and practice of the indicator was guess work. It is of Mr. Wood's practice that I say if it does not remind us of the words guess work, it certainly does not indicate any very fine engineering qualifications. Next week I shall enter into the use and practice of the indicator. Edward Malbon.
"ALEXANDRA'S" DESIGN FOR A SALEABLE UPRIGHT PIANOFORTE. [58.] Sir,—I fear, so far from makiug that portion of the case of a piano which is above its keys of the unusual, though not unprecedented, form which our Princess proposes, it would render the instrument yet more unsaleable than an ordinary cabinet Gft. high, at least until it became fashionable ; for anything in the fashion, however it may sin against good taste, is certain to become popular with her sex. I, for one, should be very sorry to make a set of four, or even a pair, on speculation. Besides, I thought I had clearly explained iu my last letter, that a man who understands his business—who does nothing without a why and a wherefore—who don't trust to bellymen, i. «., sounding board makers and string coverers, to do as thty please—finds no difficulty in making a good bass to a piano 4ft. high.
"Alexandra's " design is not novel. It is simply the tail-end of a short horizontal grand stuck upright- Harpsichords and upright grand pianos were made of siinilar form during, if not before, the eighteenth century—not to mention that the form, as figured, of the Clavicvtherum, the oldest stringed instrument with keys of whioh we possess a representation, is very similar in design. About 1&45 Mr. Mardon constructed a piano of similar form.
The Euphonicon pianoforte patented in 1&41, by Steward, whose design for a grand lately appeared in the English Mkchanic belongs to this class, but it ha* no external ca**. Its strings are exposed to the air like those of a l***pj>being supported on a very ornamental metal frame. To ray taste the design does inrinit* credit to the patentee.
Personally* my perhaps uncultivated taste prefers the ordinary tall cabinet pianoforte, when its case u well designed, and all its parts duly proportioned, to either the Euphonicon, which, from the exposure <■■*. its strings to the atmosphere, must be very liable to gel out of tune, or the elegantly designed piano of Mardon. The whole generation, with the single exception of the upright oblique grand, which had two bent sides, have, to me, a lopsided character. But this is a mere matter of taste, and as, with some personal suffering, tt«y taught me at school a small smattering of Latin, I Tuj say—" Dr. guttibu*" Ac,
However much increasing the length of the strings may improve the bass, it don't in the slightest degree improve the treble. Now, as I know very well how to make excellent basses with strings 8ft. Pin. long, though it is far easier to make yet better basses with string. 5ft. long, there is no inducement to make instruments taller at the bass than at the treble end. It is the improvement of the latter which is the great, if not the one thing needful.
With regard to what I somewhat presumptuously termed the harmonium of the future, I must plead that I am a mere snggestor. If " Alexandra" fancied she heard the familiar "ring" of the Blacksmith's anvil in my letter on "The Harmonium," 'tis no wonder after a friendly intercommunication of 22 years on this and kindred subjects; and I accept her imputation as, though an unintentional.yet agracoful compliment. I am not a harmonium maker. In regard to the manufacturers of those instrument*, I bear a similar relation to what my old friend the "Harmonious Blacksmith " bears to the members of my own vocation, excepting that I trust I am rather less "crotchety" than he is. But n* import*. \ make hirp pay me for his crotchets at a far more liberal rate than the public pay for their crotchets, and quavtcs too, when they can purchase three of Beethoven's pianoforte sonatas for the ridiculously small sum of Is., or a whole set ol 45 of the same composer's delightful waltzes at a similar price.
W. T., Pianoforte Tuner aud Repairer.
BICYCLE RIDING—A SURGICAL OPINION AS DESIRED.
 Sir,—I am nn experienced hospital H general surgeon, and not a bad anatomist. I believe that bicycle riding is less likely to produce hernia or rupture than running, leaping,"rowing, or other violent exercises which cause tension of the abdominal muscles with fnll extension of the thighs upon the trunk. On the contrary, I believe that the position in bicycle riding is that least likely to produce the injury. This opinion is founded on the anatomy of the parts, and as a practical test I would unite communication from any person who may have become ruptured by bicycle riding.
The origin of the prejudice is that the old dandy. horse was highly calculated to cause the accident, but in its use the feet pushed the road at a point oehind the vertical line of the body, and so the abdominal rings become most exposed to danger.
I am, in a small way, a bicycle rider, and encourage its use in moderation. I have frequently advised it for exercise and recreation for those engaged in office business with small salaries not affording a horse.
I could make my own bicycle much more useful. if popular prejudice did not still consider such undignified for professional men. The proposed broad band round the waist, like the soldier'B belt, tends to rupture.
Ireland, July 11. Country SurgeOx.
THE HARMONIUM.-"J. C. P." AND "ALEXANDRA."  Sib,—In reply to " J. C. P.," who requires information about the best forms of reed organs, I am sorry to say I have not much of that same to communicate, but the little I have, he is quite welcome to. I may add, that the reference I make to patents, Ac, may very probably put him ou the track of additional information. Myers's patent, containing a specification of the means of varying the pitches of reeds throughout the entire compass of the instrument at once, is No. ttln4, price Is. lOd. I have not much faith in the possibility of carrying this out in practice, because, from the difference in the lengths of the reeds in the bass aud treble, and the fact that those differences in length are not the only means employed to produce the required succession of sounds, I cannot conceive how to make the compressors, which alter the vibrating length of each reed iu an Eolophon or harmonium, so that they shall raise or lower the pitch of each one reed the required amount in relation to the others; but if J. C. P." procures and reads this and the other authorities I shall refer to. he will cheaply acquire an amount of information which I could not communicate without occupying a larger space in the English
Mechanic than I should be justified in doing on a subject of not very general interest. Indeed I have lately occupied so much of that space on musical and other Subjects, that I think it is quite time I exercised a wise discretion and occupied less of it with my many lucubrations. I hare not quite forgotten Mr. Spence's designation of me as " the universal letter writer.''
Day and M tin dies* patent, No. 50(tt, price 10d. (my
own Eolophon is constructed on their system of air
chambers or short pipes composed with free reeds).
Wheatstone's patent, No. 10,041, price '2h., describing a
combination of reeds and air chambers in the form of
stopped pipes placed a considerable distance above the
free reeds, which, under these circumstances, induce
powerful resonances in the masses of air contained in
those pipes or air chambers, will afford him much
practical information and food for thought. Yet more
13 contained in Wheatstone's patent, No. 10,041 price,
ms. on what may, in contradistinction to free, be
fairly termed string reeds; for although Wheatstone
was not the first inventor of these (Professor Robison
■was ;—see his Mechanical Philosophy edition of 1804), |
lio was their great improver, for he showed how they
could be made to titter not only the reed tones proper
to them but also to cause the vibrations of a tobh
tVharmonie, or trne sonndboard, and thereby compel it
t " ntter its own sounds in unison with, and in addition
to the reed tones. While on Wheatstone I have much
Sleasuro in bearing testimony to the fulness and luciity of his specifications: he leaves nothing to the reader's imagination, but makes, by his drawings and unusually clear descriptions, the matter plain to the M meanest " capacity—my own for instance.
May I pre*nme to give " J. C. P." just one little bit of advice, and that is to endeavor to carry out our Princess Alexandra's idea, and make an harmonium which shall deserve—from the great variety of tho timbre of its different ranks of reeds —the title of wind "organ?" Nothing polls like monotony. Noftonbt the harmonium of tho future suggested by my friend "W. T." is not a small affair; but then his ideas are based on his familiarity with such instruments as the organ at the church of St. Sepulchre and similar anything-but-small instruments, but I think I can see pretty clearly that both he and the Princess are quite right in their demand for variety of timbre, so I should recommend "J. C. P." to go in for something like it, and provide bellows—Qy. more than one—-large enough to enable him to add half a dozen ranks of reeds at any future time when he has tired of the familiar tone of his first loves.
Before commencing operations, let me earnestly entreat him carefully to examine the professional harmonium advertised in several Nos. of the English Mechanic, and probably deservedly commended by Mark EUor: also the best productions of Alexander, Ramsdeu, Evans, and last but not least, of Herman Smith, who has afforded the readers of the English Mechanic So large an amount of practical information —which I trust " J. C. P." ha^ rend—and who promises yet more, for which I hopefully and anxiously wait. I also jacommen-1 liim to use every opj>ortnnityof picking up knowledge by reading and observation of the practice of the mastered* this action the principle of the wise pt ■«< ipt, ** in all thy gottings get knowledge." (NB. If you can get money also, so much the better) too. Forjraauv jrear I have carried this precept out in the matter of "strynged" musical instruments, the pianoforte especially, but I am yet, notwithstanding a pretty extensive experience—very glad to avail myself of the practical experience and ability of my fellow correspondent "W. T." (By the way I see, "Alexandra" says, that when writing about his harmonium of tho future, he signed "R. T.") to carry out my crotchets ; for after all, we amateurs, however clever we may be, or rather think ourselves, at the thinking business, are usually poor hands at the practical.
The Harmonious Blacksmith.
THE EARLIEST OP PIANOFORTES.
THE MANICHORD—QUERY, WHAT IS IT?  Sir,—This instrument, aud many of its predecessors, is figured in RinibauHs "History of the Pianoforte," and he thinks it was simply an extra long and superior kind of clavichord. The manichord most not be confounded with "yo mono chordis," which seems to have been simply a name prevalent in Scotland and elsewhere for the clavichord. I have little doubt the manichord was a species of clavichord, differing from the ordinary instrument of that name in the construction of its tangents or string strikers.
Probably there were two clavichords, the one with clothed tangents aud the other with its tangents of uncovered metal. I strongly suspect the latter is the instrument whose name used to be written clarichord, from the French word clair (clear), for its tones would be much brighter than those of one whose tangents were clothed, even if only with vellum. The fact that no clavichord with clothed tangents has come down to our time is no proof that such never existed, for their clothing may in the course of perhaps centuries have perished, just as the clothing of the action of tho piano often does in a few years, with the assistance of moth.
Although I have not seen an ancient clavichord with clothing on its tangents, I have seen a modern one. About two years ago one of this kind, of German make, which belonged to the late Mr. Prnwse, was sold by Messrs. Puttick & Simpson. I traced it to the possession of the bandmaster of the Royal Artillery, but could not recover it. I suspect this is properly "a modem manichord, and that by simply taking the leather coverings off its tangents, it would cease to be one, and become a clarichord.
The Habmoniocb Blacksmith.
102] Sir,—Considering that the keyboard was employed to open the valves or pallets which admit air to organ-pipes at least as early as the ninth century, it seems rather improbable that tho same contrivance (probably rednced iu, width to suit the fingers instead of the fists of the never-to-be-forgotten "organ-beater," whose descendant* are far from extinct until this day) was not employed to put iu motion the strings of musical instruments designed on the model of the harp or the cythera. At a period of probably a thousand years ago it is quite likely that this was done in those eastern countries in which the pipe and free reed organs have been known in a more or less complex form from a period anterior to any historic records we are acquainted with. Our ignorance of such records is at best only negative evidence of their non-existence, or that stringed musical instruments, surrounded by manuals, had not been constructed—an assumption based on the too common fallacy of making our ignorance a measure of possibilities. As well might it have been assumed that America did not exist, because centuries elapsed before Columbus re-discovered that division of the earth; and, as the knowledge of its existence had died out, a geologist of the period, with that turn for hypothetical speculation, if not for logical deduction, which distinguished the predecessors of Lyell, might have learnedly proved (to his own satisfaction at least) that (like Venus anno domini) what used to be termed the fourth quarter of the world had just risen from the sea. N.B.—Mathematics had not at that early period been sufficiently developed to enable us, by a very different kind of calculation to that denominated the differential calculus, to "kalkalate " that Australia was n fifth quarter of the globe. It would be well for us if our astute Chancellor of the Exchequer could, by a similar "kalkalation," repeatedly convert four quarters' taxes into five, for then a handsome surplus would be the normal condition of revenue, and wo might hope John Bright's siimuinni bouum Of earthly happiness, "a free breakfast-table," might soon be realized. Verily our stout Quaker thinketh of carnal things.
The earliest keyed musical instrument with strings of which we have any record is the keyed cythera or clavieythernin; and its earliest known representation exhibits it standing upright, just as if some clever fellow of the period did what was afterwards patented in England about lHOl)—rim, put keys to a harp. Unfortunately the patent rolls of that early time, when clavicythera were made for love or money, have not been found either in that receptacle for unarm antiquities, the British Museum, or anywhere else that I am aware of; so I cannot at present determine the interesting question, whether King Nebuchadnezzar, when tired of the cares of state, set us the first recorded example of "monarchs retired from business" (by the way, I fear Dr. Doran forgot him), and wisely recruited his exhausted energies by a diet "intirely vegetable," as those innocent advertisements of vegetable rank poisons express it—I was saying that whether he, under the circumstances of his forced residence in the country (I mean when like my horse he was "put out to grass" for the season), solaced himself with his clavicythernm as Queen Elizabeth said she did with her virginal (T fear in her case female vanity had something to do with it), we have unfortunately no means of ascertaining ; for the writings of the harmonious blacksmith of that early period have (if ever they existed, I have not seen them > as certainly perished as those of the somewhat garrulous person who had that title imposed on him in early life will do when something better is written (N.B.—Doing this would be far from difficult] to more worthily occupy the place in our journal which his writings don't deserve.
In the clavicythernm the strings were treated like those of the harp, the flute, the guitar, and modern unsuccessful students are "until this day"—i. «., they were plucked. I only hope the latter, who are not invariably saints, ntter as sweet sounds when they undergo (for their good) this very needful process, as tho musical instruments enumerated do, and that the said students don't become "instruments of wrath," or ever utter sounds associated with the idea of "condemnation." When the clavicythernui was laid on its side it became the spinet, and when the spinet was put into a rectangular case it became tho virginal. Both gradually developed into the harpsichord, certainly the king of its class; but perhaps I am a partial judge, aud I confess to a weakness for one of my early loves. It is not needful I should describe so comparatively well-known an instrument here, for I have done so at pretty considerable—perhaps rather too great—length in my appeal for the earthly salvation of ancient musical innocents from the Heroddike destruction they undergo from the modern Goths and Vandals, who work their wicked will on them, to the great sorrow of collectors, who would bo willing to pay almost any ransom to rescue them from their captivity among those barbarians. The whole generation of harpsichords, spinets, Ac, whose strings are plucked by plectra not held in the hand, or by the finger itself, were deficient of the power of expression, until other means of causing the vibrations of these strings was resorted to. The example of the various harmonicas, as for instance, that formed of pieces of wood (probably tho most ancient of all), which has risen from the dead with a new Greek name, Xylophono (N.B. It has very little "phone " in the musical sense, and its sounds have a strong family likeness to those elicited when Punch's wooden cudgel comes in contact with the almost humanly wooden head of another puppet—it is far inferior to the old wooden harmonica in the East India Museum) and yet more that stringed harmonica the
substitution of a aatnxnsr for a plectrum, aud this produced the first " forte piano," with keys, for, in truth, all the harps, lutes, cytheras, and dulcimers, were true pianofortes in the musical sense—i.e., they were capable of expression, and, therefore, piano fortes in the musical sense of those words.
The earliest pianoforte with keys of which we know any examples is termed the clavichord, probably from clavis, a key, and chords, a string. I have before fully described this instrument, so I refrain from vain repetition. Whether the hammer which strikes the string be rigidly fixed in the key or detached from it, so long as it is a hammer, it enables the performer to vary the loudness of the sounds—i.e., to play with expression, which a plectrum moved by a key does not, hence all hammer instruments are true " forte pianos.''
It is by no means certain that, although the earliest now known, the clavichord was the earliest of hammer instruments; it is at least probable that some action more resembling that of the drumstick, or the striker held in tho hand of the dulcimer player, preceded the tangent. Making the striker or hammer perform the function of a bridge rather seems a refinement which could hardly occur to a performer on the dulcimer who was compelled to lift up his striker immediately after he had struck the string with it, or he would have produced the effect termed blocking by pianoforte makers. Perhaps on the principle that all discoveries are said to be accidents—which, by the way, is the gross error, they are far oftener the result of profound thought and careful experiment—the tangent of the dulcimer may hare been suggested by the falling of a hard body (a thing I hope I never may become, I prefer being sneered at as the "soft body," it sympathy for the suffering of others deserves that title) across the string, and at once putting it into vibration and, by shortening its vibrating portion, raising its pitch. It did not require a remarkably clever artist to transfer this effect by employing a striker—i. e., tho tangent, fixed in the key. I thiuk (although but a " soft body ") I could have done nearly as much myself; but then it is so extremely easy to set the egg upright when some one—too often utterly forgotten—has broken its end ready for you. Many great reputations are very cheaply made in this way; but man has a perverse proclivity to set up idols and shams for worship.
The earliest hammer harpsichords or pianofortes, in the modern technical sense of the word, of which any known record exists, are those made by Christofali, of Padua, in or before 1701. In these (which are fully described, and their action figured, in the "Giornale do' Litterati d' Italia," A.d. 1711) the hammer acts like a drumstick, or the striker employed to vibrate the strings of the dulcimer—i. e.t they rotate on a hinge or centre. So, in the modern technical sense, Christofali was the first pianoforte maker on record. It is remarkable how far this early Christian father of pianoforte makers, yclept Christofali, was before his time; for he especially says that this kind of harpsichord ought to have much thicker strings than those of the ordinary sort. He also anticipated some of the most supposed comparatively modern important improvements in the action, especially the escapement of the hopper or hammer lifter, aud allowing the hammer to fall into an acnte-angled receptacle, thus preventing it from rebounding to the string by a contrivance which is in principle the same as that afterwards re-invented by Robert Stodart, and patented under the name of the check.
I have already said that to produce a true forte piano, in the musical sense, the hammer need not be detached from the key. Neither is it absolutely essential that it should rotate on a hinge or centre: in a word it need not, except as a matter of practical convenience, be a lecer. It is obvious that if the tangent of the clavichord were guided by two sockets, similar to those which guide the damper wire-stickers of a piano, and its edge kept at the right angle with the string, it would act even better than it does when fixed in the key; for then its path is not quite rectangular, but really a circular arc whose centre is the key balance. Like such a tangent, a sticker, whose top surface might be of wood, either clothed with leather or felt, or not clothed at all, similarly guided, could be employed to strike the string ; and if the key were prevented by a back touch or otherwise from lifting the supposed sticker with rectangular motion quite up to the string, its path would be completed by its momentum — it would strike and rebound from the string. This extremely simple action was not I believe evolved out of the depths of my consciousness, as Kant would have expressed it; but, if I am not mistaken, it was actually used by Marias, in one of his three clavicieu-. a mallet A.d. 1710. It seems to be the rule "in that case made and provided," that old things shall be reinvented and letters patent obtained for them. This not very valuable invention, in the practical sense, was no exception to that good old rule; for, in 17B7, Master Humphry Walton (not him of the clock) patented a combination of it with the ordinary hinged or centred hammers. It does, indeed, seem a strange way of striking the strings of a piano to do it by means of punches—for this is just what Walton's perpendicular hammers are—which punches are themselves struck by ordinary hammers. The much older plan of hitting the strings with the hammers themselves seems at once simpler and more effective, bat we must not be too severe on poor Walton: perhaps he was actuated by the best of motives; and, as he was prevented from using the check by B. Stodart's then existing patent right, he benevolently devoted his ingenuity to contrive something .producing the same result as Stodart's invention, not within the purview of his patent, which might afford the musical public similar advantages without that public being wholly dependent on Robert.
suutir, which we call dulcimer, naturally led to tho | Stodart, Nevertheless, Master Walton seems to have