tate the varnish were perfectly successful, and he
gives the following directions for the preparation of a
composition which closely resembles the true Chinese
article. First of all, two parts of copal and one of BRIGHTON AND SUSSEX NATURAL HISTORY
shellac are to be melted together to form a perfectly
fluid mixture, then two parts of good boiled oil,
removed from the fire, and ten parts of oil of tur-
pentine are to be gradually added. To give colour,
the addition is made of solution in turpentine of
gum gutta for yellow, and dragon's blood for red.
These are to be mixed in sufficient quantity to give
the shades desired.

diamond-boring machine is four men-one to each made hot, are to be added; the vessel is then to be held on the 23rd ult., Mr. Glaisver. Vir

peared from his history, was unable to bear much fatigue. It does not appear, however, that he suffered from any ailment to which the unusual arrangement of his internal organs in any way contributed. The transposition of the viscera is certainly a sufficiently rare occurrence to warrant a notice of the point. We can only regard such abnormal arrangements as are occasionally met with as strange freaks of nature, with no appreciable influence on the health or habits of their subjects. It seems a strange circumstance that, in no instance that can be discovered, has an abnormal arrangement of the viscera, as the result of natural transposition, been ascertained, or even suspected during life a fact which would argue one of two conclusions, either the extreme rarity of the cases, or the exceptionally good health of those who are the subjects of such transpositions.

THE ROYAL IRISH ACADEMY.

Ar the last meeting of the Royal Irish Academy, June 13, Dr. Sigerson, F.L.S., read a paper entitled "Further Researches on the Atmosphere."

In order to obtain an accurate knowledge of what is usually and what is occasionally present, it appeared requisite to make a careful examination of particular atmospheres as well as of the general air. After detailing his mode of operation, he proceeded to describe the objects found in the sediment from the air taken from ledges above man's height, and observed likewise in the atmosphere. Iron-factory air, a friable black dust; on examination, this was found to be made up of particles of carbon, of ash, and of iron. The carbon formed the largest masses, the ash-particles were reddish, or white and opaque. Some transparent pieces with a glassy fracture were noticed, and were regarded as glass resulting from the fusion of sand used in the welding process.

flax is "scutched'

The results of the study of the several other atmospheres, and their effects upon the health of those abiding in them, were described at length. A brief summary is all that can be given here. In "shirt-factory air," fine filaments and fragments of cotton and linen were found, with a few minute ova, not generally dispersed. The girls employed in the factory had become snuff-takers. In the atmosphere of "threshing-mills," fibres and fragments of chaff, awns, grain, together with some smut-balls, were found. In that of oat-meal mills, fibres were seen in unexpected number, together with minute fragments of the pericarp of the caryopsis and starch-granules, with a rare spore and an acarus. This air was not so injurious as that of "flour-mills," the dust being less. The atmosphere of mills where was found to be so bad, that these mills could only be regarded as human slaughter-houses. In the air of printing-offices, from various symptoms observed, antimony was believed to be present. In consequence, some dust taken from a rafter eleven feet above the floor was submitted to the secretary of the Academy, Professor W. K. Sullivan, whose analysis confirmed the accuracy of the expectation. Antimony was found ?? were and no lead. In the "atmosphere of stables found moth-scales, some larva, eggs, spores, and a great quantity of cuticle-scales and fragments of fine hairs, with some corpuscles and fragments tinged blood-red. An acarus was present in the dust. Hairdressers had a similar atmosphere, so far as distinctive elements, scales and hairs, were concerned. The "machine-brush" increased their amount.

Tobacco-smoke, with some difficulty, was got under the microscope. It was examined on entering and on leaving the mouth. Little globules of nicotine were discovered twirling and flitting about in it, like monads. Some remained on the walls of the mouth; when the smoke was breathed (by novices), more globules were retained in the lungs, and nausea and illness supervened. These globules, if found in the air, distributed by a cigar-smoker, might be mistaken for germs, as they would resist the iodine-test for amyloids.

were

ex

3rd. That the theory of the panspermists seems 4133). With regard to the former, I may perhaps be forunfounded on fact-that there are no hosts of germs given for saying that, as it stands, it has to me no always floating about in the atmosphere, invisible meaning whatever. With respect to the latter, if your and maleficent as genii of Eastern stories. Air is correspondent will turn to p. 649 of Vol. 10, and to not much better, but not generally worse than pp. 1 and 2 of Vol. 11, he will I hope there find the explanation which he seeks. water.

Mr. G. Firth is good enough to criticise my very un"Astronomical Notes" for June. It is

5th. The "germ theory" asserts "that epidemic
diseases are due to germs which float in the atmos-pretending
phere, enter the body, and produce disturbance by
the development within the body of parasitic life." It
is opposed to the opinion that epidemic diseases are
propagated by a kind of malaria, which consists of
organic matter in a state of motor-decay. It is sup.
posed to be supported by certain statements about
the non-occurrence of putrefactive changes in closed
vessels, which have been disputed and by the
statement that retten malaria cannot act like leaven,
because fermentation is caused by the growth of the
yeast-plant. Now, the effect of the growth of
parasitic plants in causing skin-diseases is well
known; if they caused epidemics likewise, their
presence would, in all probability, have been as

soon detected.

THE NORTH STAFFORDSHIRE NATURAL-
ISTS' FIELD CLUB.

THAT portion of the Valley of the Manyfold which
is nearest to the village of Wetton, was chosen for
the third meeting for the season.

The party struck the valley, not far from
the once celebrated Ecton mine. At a cavernous
opening near Wetton Mill, Mr. Carrington,
the veteran geologist and barrow-digger, was
superintending an excavation in its floor. No
proof was obtained in the shape of fragments of
charcoal and such objects that the hollow had ever
been inhabited by primeval man, but only clay and
water-worn boulders of millstone grit, no doubt
carried in when the surface of the country was very
different, and the rivers larger and at a different
level to what they are now. Pebbles from the same
formation (the millstone grit) were pointed out by
Mr. Carrington adherent to the sides of the lime-
stone cavern. Later in the day bones were dug out
of the clay, especially one large vertebra. In the
cavern Mr. Carrington read a short paper on the
duties of a field naturalist. He ended by exhibit.
ing his original pen-and-ink sketches of the articles
exhumed by himself in the floor of Thor's cavern,
towards which the party now directed their steps.
The instruments discovered were of the Romano-
British period, in stone, bone, bronze, and iron.
The cave was not a true bone cave, like those of
Gibraltar or Kent's Hole for instance, with bones
below a layer of stalagmites or imbedded in it, nor
did it yield traces of primeval man, such as weapons
of flint, but it appears to be a water-worn hollow
filled below with clay and stones rounded or
smoothed by water-transport or attrition, and more
recently the haunt of our British forefathers.

quite right as to the pleonasm involved in the employment of the word "a.m. on the next morning," I have no means of knowing whether it was a lapsis calami on my part, or a printer's blander. Certainly I am not responsible for the 7h. 12m. to which your correspondent refers, save to the extent, perhaps, of making my 1's and 7's something alike. The word "afternoon" though, in the context, would suffice to show most people that 7 o'clock could not have been intended, as that is an hour usually and conventionally ascribed to the evening. With regard to Mr. Firth's remarkable peroration, it may suffice to say, that as the so-called signs of the zodiac are only twelve divisions of the ecliptic, quite irrespective of any stars whatever, it certainly seems to me in my weak-minded way-that the position of a planet can be better given by referring it to a known and (practically) unalterable constellation, then to an abstract and impalpable line. Doubtless the precession of the equinoxes is (from the Firth point of view) very annoying; but still, as an obvious result of the law of gravitation, I do not quite see how it is to be got rid of; and as its sole object, pro hac vice, is to shift the origin of certain imaginary co-ordinates, I am unable to see what good I, or any other astronomer could do by asserting that a planet was in such and such a "sign," which no one could see, instead of saying that it was in a given constellation, known and visible to everybody. Does Mr. Firth imagine that the readers of the ENGLISH MECHANIC would find an object more readily from so eccentric a description? A FELLOW OF THE ROYAL ASTRONOMICAL SOCIETY. [1]

"BARTON'S PATENT SELF-ACTING FEED

WATER HEATER FOR STEAM BOILERS." SIR,-On page 302 of the ENGLISH MECHANIC, June 17th, I observe a portion of Mr. Baskerville's letter devoted to criticisms on Llah's or Hall's economiser, implying doubt as to the general efficiency and economical results of feed-water heaters. He says, "The temperature of the waste steam escaping from a non-condensing engine is 212 degrees or so, and that is the maximum of heat it can impart to the feed-water passing through it, but as a matter of fact it never does so by many degrees." So much depends upon surrounding circumstances in connection with this question, it would be premature to fix any given standard of heat to the steam at the ontlet of the exhaust. Expansion of steam after cut off, reducing its elasticity, and consequently loss of heat, with distance from cylinder to exhaust outlet, may be said to form primary cause of variation in changing the temperature of exhaust steam imparted to the feed water. Deductions and calculations made by figures, from a scientific point of view, are all very well in theory; unfortunately they do not always harmonise in practice. Again he says, "There is no appendage of the steam engine which is less understood than the feedwater heater." This we quite agree with. If it were better understood, it would be more largely adopted, to the great satisfaction of steam users generally. I can assure Mr. Baskerville (whatever his figures may say to the contrary) that the "inevitable" 25 per cent. saved in fuel is not "a delusion," but a practical fact with feed-water heated to 212 degrees. I have, by careful and trustworthy experiments, proved the truth of those statements, by weighing the coal used week for week, doing the same amount of work with the engines in both experiments; that is to say, one week with cold water, the other week with water heated to able to J. PASSMORE EDWARDS. All Cheques and Post Office Orders to be made pay- 212 degrees by the economiser; in all cases the statements have been fully confirmed. Having had charge of one of these heaters for over twelve months ("Barton's," as represented by the above illustration),

LETTERS TO THE EDITOR.

[We do not hold ourselves responsible for the opinions
of our correspondents. The EDITOR respectfully
requests that all communications should be drawn
up as briefly as possible.]

All communications should be addressed to the
EDITOR of the ENGLISH MECHANIC, 31, Tavistock
street, Covent Garden, W.C.

"I would have every one write what he knows, and this only, but in all other subjects: For such a person as much as he knows, but no more; and that not in 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.

ASTRONOMICAL.

SIR, There is a small comet (D'Arrest's) in Serpens now; but "W. R." (4084) p. 335, will scarcely see it with the naked eye.

J

STEAM OUTLET

EXHAUAT STEAM.

H

A

COLD WATER
SUPPLY..

In order to arrive at the cause of the ill-health of "tea-tasters," their special atmosphere was amined. In pursuing their avocation (selecting teas), they had to take a sip with quick inhalation, and thus a small shower of fine tea-drops entered their lungs. On examination of such tea-drops, a considerable quantity of fibro-vascular and cellular tissue, from the leaves, was found which might aid to tease the lungs. But the real agents of mischief The extract given by "Foreigner" (4180), p. 358, numerous droplets of essential oil, very plentiful in Assam tea, which was particularly from a Brussels paper, is just a little obscure. How in " can be severe on the tea-tasters. Nausea, disarrangement the world a comet on the East of the Sun of the nerves, and sometimes syncope afflicted seen "after midnight" passes my very limited comprehension. I have heard nothing of this comet of Winnecke's, inasmuch as the circulation of an Ephe- I will, Sir, by your permission, endeavour to enlighten meris of a newly discovered one among the English your correspondent on what he calls the overrated observatories, is quite beneath the dignity of the editor results of these contrivances. The fallacy of using of the Royal Astronomical Society's publications. We theoretical argument in opposition to practical results are only too thankful, as a body, to get our " Monthly requires no further comment. Notices" a month after the meeting at which the papers they contain were read. It is only some radical and revolutionary spirits who have dared to hint that we are entitled to early intelligence of recent discoveries in the heavens; but these obtrusive people, however, are crushed out by the sublime indifference of the editor referred to.

them.

As a result of numerous observations, some of which are here recorded, Dr. Sigerson considered himself justified in drawing the following conclu

sions:

1st. That stomach signs-irritability, nausea, dyspepsia are frequently symptomatic of interference with the lungs; so that the stomach, in such cases, may obscure the symptoms, but will not cure the disease.

2nd. That the lungs have a power, not hitherto suspected, of absorbing or assimilating even solid matter.

it, thereby securing the constant supply of feed water. The engine blowing the exhaust on the water in the heater under my charge is 14 horse-power nominal, pressure on the boiler 40lbs. to the square inch, making 60 revolutions per minute, length of stroke 2ft. 6in., cutting off at half stroke, passing through the heater about 6,000 gallons of water per day, with a continuous temperature of 212 degrees.

tance, with the considerable focal length of the component lenses in your correspondent's possession. I may add that I do not believe that the dimmess of which he complains has anything to do with the interval separating the two combinations in his eyepiece, which, as I have said, admits of considerable variation. If his object glass be not faulty, I should unhesitatingly attribute the defect of which he complains to the disarrangement or imperfection of the little stop between his third and fourth lenses. The adjustment of this must be made with scrupulous care, and the opening be of just sufficient size to let the crossing rays B. Pipe for conveying exhaust steam into the water. pass through it. If it be too small it will diminish the C. Tap for cold water supply. effective aperture of the object glass. If it be too large it will let a quantity of false light through, which will fog and obscure the image. I question the ability of any one possessing the somewhat limited knowledge of your querist to make this adjustment for himself, and should advise him, by all means, to send his eyepiece to some working optician.

The efficiency, simplicity, and durability of this heater will be best understood by consulting the following description. (See diagram.)

A. Tank for the heated water.

D. Float.

E. Test-rod.

F. Hot water supply for the feed-pump.

G. Pipe for conveying away the surplus steam.
H. Guage showing the height of water.

I. Thermometer showing the temperature of water.
J. Man-hole.

K. Lever for opening tap C.

L. Cold water supply-pipe.

C. Tap which is coupled to a lever K and float D, where the water in the heater raises the float D, and closes the tap C, and so reduces or shuts off the supply; and when the water-line is lowered by increased with drawal through F, the float D falling, and opens the tap C, augments the supply of cold water flowing through C. The nozzle of the tap C is arranged to deliver into the bell-mouthed steam-pipe B, directly on the cold water heating to boiling point. E, test rod, whereby it can be ascertained, without removing the man-hole J, whether the tap C is working freely. It is impossible for the tap C to get out of order, for every stroke the engine makes it moves the plug C.

When we consider the extent to which as a nation we are dependent for our commercial prosperity on steam power, and that this power is increasing every day, prejudice, or lack of information ought not to stand in the way of any modern invention, having for its object (as this invention has) the improvement, if not the perfecting of a system the want of which has long been felt. The many existing proofs sent to the patentee, Mr. Barton, in the form of testimonials, as well as verbal declarations personally made of the great utility as an economiser of fuel and water, would in themselves be a sufficient justification for its introduction to the public. There are other results, as follows, though of less importance individually, yet no less momentous

as a whole.

1st. Its safety to the boiler, by preventing the sudden and unequal expansion which takes place when cold or partially heated water is introduced.

I may answer "Uranus" (4109), same page, by
telling him that Chance's price for their warranted
optical crown and flint glass of the size that he re-
quires is £7 48. per disc, so that a pair of 6in. in dia-
meter would cost him £14 8s. His trap tools may be a
little larger in diameter than his lens; his polisher
should be rather smaller. He may go on grinding his
lens with very finely washed emery until the image of
a candle can be seen in it. He can then transfer it to
the polisher. I have strong reason to believe that
alpaca is the best material for that polish. I really
cannot tell how many hours a lens occupies in taking a
polish, as I have never worked at one except in a
desultory way, but I know that polishing is very
tedious work. Some of our opticians, who can speak
er cathedra on this subject, may probably give
"Uranus" the information he requires on this sub-
ject.
Regarding the inquiry of "Urban," on p. 881, as a
quasi-optical one, I may tell him that my knowledge of
bisulphide of carbon prisms is to a great extent theo-
retical, my practical experience of them having been
contined to the employment of two belonging to a
friend.

"W. C." (4132), p. 358, has done pretty fairly in seeing Jupiter within 9° of the Sun with his 84-inch mirror-albeit, he has not achieved anything very surprising. I have more than once seen Venus with a much smaller instrument, when the glare of direct sunlight was just beginning to be perceptible in the field. I do not think that he would see Mars any nearer to the Sun than he could see Jupiter, but Mercury he certainly ought to be able to follow nearer to the Solar limb. He will find a very constricted field a great help 2nd. By relieving the engine of back pressure pro- in viewing a planet under such circumstances. duced by heaters of other construction. By purifying "E. G." (4166), also on p. 358, can do nothing with the water, and precipitating deposit before it enters the his object glass. It must be re-ground and polished to boiler. By using the exhaust steam for heating the feed-get rid of the scratches upon it; and this, if it be of water, and giving to the boiler a regular supply at any value, would assuredly ruin its figure. The proboiling point, thereby saving 25 per cent. in fuel. It cess of grinding and polishing has been described over supplies a practical safeguard against explosion, by and over again in your columns, but is certainly making it impossible while the engine is running to in- beyond the capability of any one who, like your corretroduce cold water into the heated boiler. It increases spondent, knows nothing at all about it. If he should the steaming and working capacity of the boiler, the choose to risk spoiling its figure he had better take his generation of steam with a given amount of fuel being glass to a practical optician, who would, at all events, much greater than when the boiler is supplied with eliminate the scratches for him. water cold or partially heated. It saves water by the condensation of steam, which takes place in the heater, again returning to the boiler. It is perfectly selfacting, thereby doing away with constant personal attention. It frees the boiler of old scale, and other incrustations, and prevents the same from re-forming. It has other advantages, and is easily adapted to engines of any construction. I know that it is becoming extensively patronised by engineers, iron forges, boat-builders, steam sawyers, and steam users generally. I see by a testimonial from Messrs. Laird Brothers, Birkenhead Iron Works, that they adopted one of these heaters some months ago, and found the saving so considerable, and the working so satisfactory, they have now applied it to all the principal engines in

the establishment.

Engineers, boiler-makers, and steam users of every class, would do well by making themselves thoroughly acquainted with the many advantages to be derived

from the use of this heater.

Though simple in its construction, it accomplishes in the most perfect and satisfactory manner an astonishingly large number of very important results. Space would not be allowed me, or I would have forwarded to you for the information of Mr. James Baskerville and others, a tabulated statement of the saving in coal and water, extending over a period of three months, with three single fire flued Cornish boilers, supplying steam for engines of 50 horse-power with a number of steam hammers. Should Mr. Baskerville or any other of your correspondents require any further information in reference to this heater, I should feel great pleasure in replying to any such request. S. CROMPTON, Birkenhead. [2]

A FELLOW OF THE ROYAL ASTRONOMICAL SOCIETY.
[3]

GAS.

SIR,-Your readers are too numerous, and like all the public, too little informed upon the subject of the production and consumption of gas, to allow such remarks as those of "C. D. E.," p. 354, to pass unnoticed; and as I happen in the course of my life to have had practical acquaintance with the subject, I take on myself to inform your readers that "C. D. E." evidently knows nothing whatever about the matter. He says, "good coal gas is rich in these vapours as it passes out of the retorts, but the gas companies find it expedient to extract a greater part of these condensable vapours and supply their customers with a very low power illuminating gas." A more misleading statement was never uttered, even by the gas quacks, who for years have made it their business to go about making false statements in order to get up squabbles between gas companies and their customers, and particularly with the corporate bodies who can pay "expenses."

The companies are bound to supply a gas of a power which was fixed as being the limit obtainable from Newcastle coals; as a matter of fact they are obliged to use a portion of expensive cannel coal in order to insure the gas being up to that standard. The vapours they remove are those which, being condensable, would otherwise form deposits of napthaline, &c., in the mains and services, and gas manufacturers are doing all they can to secure these vapours being made into conden

sable gases.

endless lights, while half the lights are allowed to burn
with ragged flames and the gas hissing away, giving
nothing like its proper light, and the fault is of course
laid upon the gas company. As to price, I can tell
Londoners as a fact, that they now pay 6d. and per-
haps 9d. a thousand more for their gas than would be
the case but for their so-called friends, who, saddling
the companies every year with the law expenses of a
parliamentary fight, put that cost on the gas, for every
effort is made to reduce cost and price, in order to in-
crease consumption. As to carburetting gas, the best
evidence that it is not a practical process at present, is
that numerous as are the patents and processes, none
have established themselves in use.
SIGMA.
[4]

THE CLAVICHORD, ITS CONSTRUCTION, ETC.
SIR, The loudness of the sounds of this, and, indeed,
all other stringed musical instruments, must, caterin
paribus, be in proportion to the force with which its strings
are struck; and as this will be, cæteris paribus, in accord-
ance with the velocity communicated to the tangent or
string-striker, it would appear that the direction of
improvement-so far as the action is concerned-will
be to insert the tangent in the key as far from what is
termed the key balance (i.e., the surface on which the
key rotates), as is consistent with a reasonable width of
case. For carrying out this it is preferable to make
the key balance as near as can conveniently be done to
the ivory, say within ĝin.; and if the strings of the
instrument be disposed like those of a horizontal grand
piano (which is far preferable to arranging them like
those of a square piano) the tangent may be as much
as three or four times as far behind the key balance as
the finger acts on the key in front of it.

With an instrument which has but little width from back to front, whose strings are disposed obliquely like those of an old clavichord, virginal, spinet, or the square piano, it is impossible to insert the tangent far behind the key balance in the bass. This, besides much weakening the force of the blow, has the disadvantage of enabling the player to press the tangent against its string with far more force than is required to enable it to act efficiently as a bridge. This evil might be cured by inserting the tangent into a lever situated between the key and the string. By this ar rangement any required velocity might be communicated to the tangent, and the force of the blow might be further angmented by loading the intermediate lever, just as the keys of a clavichord with its strings arranged like those of a harpsichord or horizontal grand piano might be loaded to any extent which did not make the touch too heavy. It is obvious that the greater momentum of the loaded key or lever must cause the tangent to strike the strings with more force than the sinaller momentum of a key only loaded sufficiently to cause it to rise can do. The ancient clavichord was capable of executing very rapid music, as is obvious from its construction; in this respect it surpasses either the harpsi chord, on which it is possible to play a melody in pretty close repetition, or even the pianoforte. In both these instruments the striker is not rigidly connected with the key, and even in horizontal pianos the hammers do not always fall as quickly as the key rises in front. Their hoppers descend faster than the hammers can follow them, especially if the hammers be supported on checks; but nothing of this kind can occur in the clavichord: its hammers (tangents) are fixed in the keys, and must descend with them, so that no keyed instrument can be made to repeat more rapidly than a clavichord, whose keys are pretty heavily weighted; but it has the defect that its sounds cease the instant the key begins to rise, for then the tangent leaves the string and it is effectually damped by its cloth. This, which is a defect when performing melodies in repeat, becomes an excellence for ordinary playing, for the sounds do not run into each other like those of bells, harmonicas, dulcimers, and other instruments which have no dampers-not to mention pianos with more or less efficient dampers, which, by the way, seldom act so perfectly as I could wish. Even when they can act, their proper action is too often prevented by that class of performers who, so long as they can make a great noise, are not at all particular about discord, and treat their suffering hearers to the chromatic scale with the damper pedal held down throughout their abominable performance.

As formerly constructed, the clavichordist had but little power to strike, but he had great power to press the strings of his instrument; consequently the tone must have been feeble and its pitch uncertain, for any increase of the pressure of the finger must have increased the tension of the string and caused its pitch to rise. By loading the key and placing the tangent far behind the key balance, we should not only greatly diminish the performer's power to produce these disagreeable results, but if the weight of touch was increased to about three ounces-which is not heavier than many modern pianos-the blow would become sufficiently powerful to put a pair of No. 22 or 24 steel A little anecdote which I can vouch for is a good wires, 27 inches long, into strong vibrations. Perhaps answer to such a statement. A certain company was for the easy performance of very rapid music, it might THE TELESCOPE, ETC. summoned for allowing condensed liquids, removed be well to keep the weight of touch within 24oz., which from the mains, to pass into the sewers, and some modern pianists would term a light touch. I have SIR,-There is a query, headed "Object Glass" marvellous statements were made as to the danger of known 8oz. used, but it is unpleasantly heavy until, (4088), on p. 335, which at the first blush is unintel- such a course. An eminent witness, who ought to like the skinned eels, you get accustomed to it. It is ligible. On reading it over, however, two or three times, have known better, asserted that the gas companies obvious that in clavichords of the ordinary construction I have a dim notion that it has to do, not with an object put naphtha in the mains to raise the illuminating one-half the force of the blow is entirely wasted, so far glass, but with the terrestrial eyepiece of a telescope, and power of the gas close to the services, and that it was as the production of musical sound is concerned, for (assuming that I understand the nature of the ques- naphtha thus inserted which was the source of the that part of the string which is damped (although it tion), I may inform "G. B." that his lenses 1 and 2 danger. "In that case," said the company's engineer, receives a blow of equal force with that which strikes should be 1jin. apart. At in. from No. 1 a stop Why do we pump it out into the sewers?" It is the vibrating part) is prevented from sounding; hence must be placed to define the field of view. His lenses needless to say the witness looked somewhat foolish. it is not surprising that the astute German intellect 3 and 4 may be placed 4 in. apart. The distance be- The fact is that almost every complaint made by gas soon devised a method of utilizing this hitherto wasted tween Nos. 2 and 3 may be varied within consider-consumers may be traced to their own mismanagement, force by employing it for the production of sound. This able limits. The farther they are separated the higher and the want of care and knowledge by gas-fitters. Bad is the principle of Silberman's Double Clavichord, in will be the power. 7in, would be a good working dis-burners are used, and small pipes expected to supply which the tangents are made to strike its strings exactly

at their centres, i.e. between its two bridges on its one or two soundboards. If four strings can be put into vibration without abstracting anything from the force of the blow, it follows that, cæteris paribus, the loudness of the sound will be doubled; and in a clavichord with such long, thick, and, consequently, very tight strings, as I have suggested to be made, the chief objection to Silberman's plan could hardly obtain, for, with its tangents four or five times as far from the key balance as the finger acts in front of it, the player will have but little power to press the strings sufficiently to raise their pitch to any objectionable extent. A very slight rise of the pitch, only just sufficient to give prominence to the melody, the ear can endure: it is not only bearable but even desirable as one means for expression, which is the soul of music, and chiefly distinguishes the perform ance of beings possessing minds from that of the barrel, whose brass fingers not only exceed ours in number but, being actuated by a force purely mechanical and always in their right places, don't ever make mistakes daring performance-a thing some of us intellectual beings have been more than suspected of doing.

of alongside as usual. The one thing needful for correct intonation is to adjust the tangent so that it shall strike the long string exactly at its centre between the two bridges on which the string rests, which are attached to the one soundboard or two soundboards. It will be seen that in the clavichord there is not, as there is in Mr. Jenkinson's plan, any risk of altering the tension of one portion of the long string which has already been correctly tuned, by increasing or diminishing the tension of the other portion of the same string for the purpose of raising or lowering its pitch to bring it into unison with the portion previously tuned. Nearly a year ago, when requested to advise "Ye Workynge Man"-then very hot, indeed, on building himself either an organ or a piano-how to construct the latter, I was tempted to repeat Punch's advice to persons about to marry, "Don't." I recommended that most important member of "ye bodie politique' to make himself old Bach's favourite instrument (the clavichord) instead. I doubt not some of my practical friends, "W. T." especially, smiled at my ignorance; but so complicated an instrument as a piano, requiring It is obvious that a double clavichord, à la Silberman, great a variety of special tools used by different workmen must be provided with dampers which can be removed (for in pianoforte making labour is greatly divided) for from its strings. The single clavichord is most effec- its production, did not then seem to me a very promising tually damped by interweaving a strip of list with its subject for amateur art. It appeared even yet more strings between one of their resting places and the hopeless than the then popular working man's organplace at which the tangent strikes them; but as this I mean musical organ. N.B. The E.M. is not only his but would permanently damp one-half of the strings of a our organ also in another sense, and a very good and double clavichord, a removable damper becomes a improving organ it is. It goes ahead" as if it knew necessity. The very best damper for horizontal strings no stops whatever, except those it puts on the progress that I know of is the one formerly used in old square of its rivals by buying them up, a process which must pianos, which is so attached to the key that the pre- in time make it a very "full" organ indeed, and I hope ponderance of the keys is utilized to press the dampers will cause its contributors to express their "scientific to the strings. To carry out this principle it is quite opinions" and to "pipe" harmoniously. To return nnnecessary that the connection between the key and from this rather long bat, I trust, not altogether unthe damper be permanent, any simple contrivance which welcome digression-since I advised my fellow workees connects them when in use will serve; but it is very (as the author of Saturday night and Saint Monday desirable that the parts may be easily disconnected terms his class) to make themselves clavichords, and when needful, so that any one individual key may be was requested by one of them to furnish instructions taken out with great facility. There are several ways for carrying out my recommendations, the subject of doing this, probably the simplest is to guide the has been brooding in my mind, and that being but a damper wire sticker by an upper and lower socket, and shallow vessel, you see, Mr. Editor, that its thoughts to have two screw buttons on it, one above and the have run over on to this paper, which contains, at least, other below a fork made in the further end of the key some suggestions how to do it. I fear my old fault of itself, which should be reduced about fin. thick at not seeing how to do a great deal for a very little money its further end, by rebating its under side for about lin. yet clings to me; and although a modern edition of a of its length. This fork should be wide at its extremity, Silberman Double Clavichord would not cost quite so and its prongs tapered for the first gin. of its length, much to make as one of Broadwood's Iron Concert so that when putting in a key it may allow the damper Grands, nor anything like the sum I have spent on my wire to enter easily. The damper is regulated by own experimental grand piano (which amount-being turning up the lower nut or screw button until the key heartily ashamed of my great extravagance-I don't is supported at the proper height in front by the damper intend even my wife to know, lest it should become a resting on the string. Should the clothing of the standing reproach to me for the probably small redampers become unequally compressed, some of the mainder of my days) I do fear such a clavichord would keys will be lower than others, and must be raised by cost a considerable sum to construct, for it would require turning up the lower screw buttons on the damper to be braced considerably stronger than any ordinary wires. The upper buttons may be adjusted to a posi- grand piano. Certainly the action, excepting its keys, tion sufficiently above the upper surface of the keys to would cost but little, and its case need not be ornaallow them to rise some distance before they commence mental; but then the latter may be the case with the to lift the dampers. The amount of this so-called case of a piano, some of which are not only plain, like "waste touch" is not important so long as the damper the cooks, but downright ugly. It would also occupy be lifted sufficiently to prevent any part of its surface considerable space, perhaps as much as a large grand from touching the strings when at its widest vibrations. square piano; so all things considered, I must not In practice it is best to allow the key to descend from boast of its cheapness in the sense of costing very little one to two-thirds its total path, so that the key's mo- money. But, then, I utterly deny that this is the only mentum may prevent the additional weight of the condition of true cheapness; to me naught is really damper being felt by the finger as an increased resist- cheap which is not excellent: cheap and nasty seems to ance. Of course these observations apply rather to me simply a contradiction in terms, for the nasty in pianofortes, in which the finger has to raise a hammer music is worse than worthless. detached from the key, than to the clavichord, in which the hammer is attached to the key; but, even in the latter instrument-the weight of whose damper head and its wire sticker is much less than the loaded damper of a pianoforte-I think it would be desirable to allow some waste touch between the key and the damper. The design of J. Jenkinson for a double treble piano is at first sight something like a Silberman Double Clavichord: both have the great advantage of enabling us to duplicate the unisons without any increase of tensile force; for it is obvious that a string stopped or touched at its centre, and speaking the octave above the sound due to its whole length, is rendered no tighter than when uttering its fundamental sound. I don't know if Silberman carried out this principle throughout the entire compass; but, if he did, his double clavichords must have been as long or longer than a modern concert grand piano. Probably the additional power of sound obtained by this system was not required in the bass, and, as in Mr. Jenkinson's piano, it was only carried out in the two or three upper octaves. Silberman's plan had one great advantage over Jenkinson's, not from any fault which can be eliminated from the design of the latter, but which is inherent in the clavichord over the piano. In the latter the hammer does not also serve for a bridge; so, to carry out Mr. Jenkinson's idea, I had to provide two very firm bridges and a bicephalus, or rather two hammers. In the clavichord these metal bridges and one of the hammers are not required, simply because the one metal hammer (i.e. the tangent) serves at once to strike both that part of the long string which is to the right of it (or above it in an upright clavichord), and the other portion of the string which is to the left or below it. This, besides its far greater simplicity, entails the avoidance of one of the greatest defects in Mr. Jenkinson's plan, viz., the necessity of tuning each portion of the long string separately. In the clavichord this is not required, because it can be tuned by apply. ing the straining force at one end only; for it is obvious that, when its vibrations are accelerated by increasing its tension, so that its pitch is raised (say from B to middle C when vibrating as a whole) the pitch must be raised from B to pitch C also when struck and stopped at its middle and compelled to vibrate in two maisonous parts, situated one beyond the other instead

I am

I am sorry I cannot yet furnish complete designs for
the construction of a clavichord. I have seen but one
since I saw the two in 1832 at Messrs. Kirkman's.
sorry to add both these are burnt. I need hardly
add I have not yet attempted to make one. Were
I to do so I should certainly carry out Silberman's
plan, at least for two octaves in the treble. Under
these circumstances it will be seen that for me to fulfil
the request of your correspondent to furnish him
detailed designs would be rather a hard task. Perhaps
if I cannot persuade your very practical correspondent
"W. T."-who is, probably, far more able than I am to
contribute a good design for a clavichord, which would
have the further advantage over any design of mine of
his special or professional knowledge-I may be tempted
to help my fellow readers to construct old Bach's
favourite keyed instrument with expression à la main.
And if I do so I will embody in my design every
probable improvement that my very partial and im-
perfect acquaintance with more than a century's ex-
perience in the construction of stringed instruments of
the clavier class may suggest to me. Should a few of
my supposed improvements make their appearance on
the stage of public judgment in the guise of what my
friend "W. T." satirically terms my crotchets, perhaps
and other of my fellow-readers will bear with them as
patiently as they may, in consideration that much music
is largely composed of "crotchets" more harmonious
than those of THE HARMONIOUS BLACKSMITH.

[5]

BRAZILIAN RAILWAYS.
SIR,-With your permission, and in compliance with
your correspondent Bernardin's request, as contained
in your journal for the 24th ult., requiring more
light upon what may appear confused remarks of mine
as given in reply to your previous correspondent
(No. 3977), I do not wish it to be understood that the
length I gave as 69 miles is the actual length of the
Bahia and San Francisco Railway. Although your
correspondent quotes an authority, yet I do not intend
to accept such before my own. I make a kilometre to
be 62,125 of a mile, but cannot allow that the above
railway is near such as quoted-viz., 183.5 kilometres.
Not having ever measured the distance of this line,
nor having asked Mr. Thompson, the superintendent at

Bahia, also not considering it worth while to go to the office in New Broad-street to ask Mr. W. Clay, the secretary, I am unable to state actually the distance. The term, as given in my previous answer, about it, "beginning at a pillar and ending at a post " is one I heard applied to it there by one of its own officials. Bahia is a city, not a town. The company is English principally. I could easily state much more than your correspondent can learn from any work that has been made up to order, and not upon the writer's experience.

Having passed some five years in the province of Bahia (principally travelling), I have stated what I know, my authority being my own senses. Trusting that these few remarks will satisfy Bernardin and yourself. J. G.

[6]

LUNAR ACTIVITY.

observations of the lunar crater Plato during April,
SIR, I have the pleasure to inclose a summary of
May, and June, 1870, in which opposite effects upon
certain spots are pointed out, more particularly on
spots Nos. 15 and 19, not observed in April (ENGLISH
MECHANIC, May 27, p. 233) and only once in May.
At present the degree of visibility of these spots is
visibilities of Nos. 16 and 25-957 and 262 respectively,
very low-only 024. On the contrary, the higher
strongly indicate the existence of local action of some
kind in these spots.
W. R. BIRT, Cynthia Villa, Walthamstow.
SUMMARY OF OBSERVATIONS OF SPOTS ON PLATO-
APRIL, MAY, AND JUNE, 1870.-By W. R. BIRT,
F.R.A.S.

The num

The June Innation having been very unfavourable for observations on the physical aspect of the moon's surface, the returns are inadequate to determine with the necessary degree of accuracy the gradations of visibility of the spots on the floor of Plato. ber of observations amount to 35 of nine spots out of the 36 now known; nevertheless, they may be combined with the observations of April and May; the number in April amounting to 118 of 17 spots, and in May to 111 of 28 spots.

The entire number of spots observed in the three lunations is 30, of which four only-Nos. 1, 8, 4, and 17were recorded by four observers, Messrs. Gledhill, Elger, Pratt, and Whitley. No. 5 was seen by the three gentlemen whose names stand first. Eight spots were noticed by two observers-not in all instances by the same two-and no less than 17 were seen by one observer only the observer, as in the case just mentioned, not being the same in every instance.

As may be expected from the unpropitions state of our own atmosphere during June, the average number of spots seen on any one occasion in that month was as low as 5, and not more than 6:29 for the three months. Excluding spot No. 1 (the standard) and No. 35 (the spot discovered by Mr. Gledhill in April last) we have 28 exhibiting variations from the annual visibility given in the Monthly Notices of the Royal Astronomical Society, Vol. XXX., p. 161. The greatest number (18) have manifested a decrease not by any means of a regular character, or of nearly similar degrees, which, if the decrease of visibility had depended solely upon a deteriorated state of our own atmosphere, ought to have obtained. The small variation of many of the 18 spots may fairly be attributed to this cause; there are, however, six instances in which the decrease is greater than 100, spots Nos. 13 and 19 having varied as much as 215 and 236 respectively.

It was noticed in the paper communicated to the Royal Astronomical Society, and to which reference has already been made as above, that spot No. 19 exhibited the largest decrease of visibility in the six lunations, Oct., 1869 to March, 1870. This decrease was as much as 374 below the degree determined between April and Sept. 1869. It is now 236 lower than the annual degree of visibility determined in March, 1870. No. 13, a neighbouring spot, has participated in this decrease next to No. 19: its variation from the degree of visibility for the first six months was 316: it is now lower than No. 19-viz., 215. It is noteworthy that these spots are situated upon a light band or streak in the N.W. part of Plato [see diagram in the Student, April, 1870, p. 161]. The neighbouring spot, No. 16, on the same streak, has not continued to participate in this decrease: although at first it declined in visibility as well as Nos. 13 and 19, it has during the last three lunations increased, and was observed during the unfavourable month of June. These facts appear to be incompatible with the supposition that apparent changes on the moon's surface depend upon changes in the direction of the sun's light upon objects, or on alterations of the angles in which the sun's rays from them meet the eyes of observers.

Ten spots have exhibited during the three lunations an increase of visibility which is irreconcilable with the idea that the larger decrease during the same period is entirely due to a deteriorated terrestrial atmosphere. The greatest increase, 177, occurs in the spot No. 25, discovered by Mr. Elger, on October 18th, 1869, and subsequently observed by Messrs. Gledhill and Pratt. The increase or decrease of visibility of a spot does not necessarily indicate, after a certain epoch, either a present or continued change in the spot itself; for as the determinations are comparative, an actual change in the spot rendering, for example, "brighter," and consequently more readily seen, its visibility during the time its brightness continues would rise, and its higher degree of visibility, so long as it was maintained, would, to a certain extent, measure the duration of its maximum, to borrow an illustration from the phenomena of variable stars; but when this brightness subsided, and during the time the spot remained at its

SPECIMENS OF TURNED WORK.

which it would spin. Thus the pole of the ecliptic has a different pole from the pole of the equator, and if we wished to find the pole of a meridian line, wel must measure 90° distance from that circle in order to find it, and we must thoroughly understand this before we venture far upon the wide ocean, whether of investigation or commerce, and in fact it is most necessary for a nautical man to be acquainted with this subject, as upon his knowledge the lives of his fellow passengers may depend. Thus, in Fig. 1, let A B C be a right