or, as we say, the total draught in the drawing frame is 216; and these 216 attenuated engine slivers, if the work has been properly done, compose a sliver at the last head which for smoothness and regularity in thickness throughout its length is far superior to the sliver at the engine head. The thickness would be the average thickness of 216 of the slivers from the engines. I say average thickness, because the slivers from the engines not only vary in thickness from each other, but are also unlevel of themselves; the fibres are in a ruffled, entangled state, being crossed and doubled over each other in all directions. Some The object or use of the drawing frame is to double a certain number of slivers together so as to equalise the different thicknesses; to straighten the fibres out parallel to each, other, so that they will the better twist together in the spinning frames. It will thus be seen that the drawing and the doubling are necessary to each other, for the drawing could not be carried out to any great extent if there was no doubling, neither could there be any doubling without the drawing. I think very little explanation is required to show to any one at all acquainted with the subject that this total draught of 216 should not be divided equally between the three heads; the draught should be easier at the second head than at the third head, and easier at the first head than at the second, because at the first head we have to contend with a rough, uneven sliver, and if too great a draught were used here we should lose the benefit that should be derived from the doubling; the fibres being brought into better order by the draught at the first head, we may increase the draught in the second head, and so on with the third head. spinners take advantage of this fact by also putting more doubling in at the last head than at the first. The above remarks are offered with a view to a better understanding of "Factory Lad's " question as to how the draughts should be distributed between 4 lines of rollers for a cotal draught of 7 in the drawing frame. There appears to be some misapprehension as to which of the three heads of drawing this question refers. My impression on heading the question was that this draught was at the last head; I did not for a moment suppose that he would have a draught of 7 in the first head; this, however, seems to have been the impression, judging from the remarks in their replies, of Harmonious Cotton Spinner" and "Mutual Improvement" (the latter of whom thinks my preparing draughts too keen), and this appears to be the right one according to "Factory Lad's" last communication; if this be so, my advice to Factory Lad" is that the sooner he reduces this draught the better, as I am quite satisfied he would find an improvement by so doing. Whatever class of cotton he uses, this draught is, in my opinion, considerably too much at the first head. I really do not see what need he has for 4 lines of rollers at all if he makes no more use of the back line than to get a draught of 117. or what is the same thing, where the length at the first pair of rollers is only increased by 1-6th towards a total draught of 7. If this is all the advantage he gets out of the back line, it is worth while to consider whether he would not find it a saving to dispense with that row altogether, and distribute this very small draught between the three lines of rollers-thus, 19 x 3:68 = 6 99, which are not very materially different from the 2 draughts he gives for the 3 rollers. Assuming that "Factory Lad" has a total draught of 216 in the three beads, and wishes the draught at the last head to be 7, I should arrange the draughts as follows:front 2nd &rd To = 216 & 2nd. & 3rd. & back. tal 1 1st head= 2·27 x 173 x 131 = 52nd do. = 244 x 1.82 x 1:34 = 6 3rd do. = 2·65 × 192 × 1:38 = 7· The arrangement in the first head is on the supposition that there is a slight draught at the engine head. The importance of this question to cotton spinners has induced me to enter at this length into the subject; as I have said in a previous letter, it is a question on which widely different views are entertained by practical men, and I am sure you will be doing good service to an important industry by allowing it to be freely discussed in the pages of the ENGLISH MECHANIC, and I hope that others will not hesitate to follow this with letters giving their views on the matter, knowing as I do that there are large numbers of readers of our journal in these districts who are well qualified to give an opinion on the matter. E. Slater, Burnley, not only appears to have mystified your readers by his first reply to" Factory Lad's" question, but from his second reply he appears to have got into a muddle himself. I cannot conceive how hefcould expect that anyone would gather his meaning to be 25 x 169 x 167 = 7055 from the figures 24 + 2 + 2 = 7, which he calls setting out the draughts equal. I have no doubt but that the "intelligent old man who told him to make his draughts equal knew very well what he was talking about, but at the same time I think the assertion would be qualified when he made it, and this Mr. Slater appears to have lost the end of entirely. The figures I gave in a previous letter, as well as those above, are founded on that rule, and it may exercise the ingenuity of those interested to find out from them what is meant by the phrase of " making the draughts equal." given by Mutual Improvement," p. 111, ranging making 64 bank roving, the spindles running 1340, them as follows: has succeeded, as I expected he would do, in finding a I am glad he has now given the wheels and rollers He says (p. 283), "Let me inform him for his edifica- near a correct result. 14 × 6 no = 1. But in cotton Now, I happen to be very well acquainted with the I If" H. C. S." cannot see how a lap can bag without To his inquiry respecting yarn testers, Mr. Samuel B. W. R. SIR,-Reading your paragraph in last week's edition, about the chaff that seems to be going on among us cottonians, I must say that I was at once struck with the force of your remarks. For my own part I shall always strive to let you have as much of the There is another matter in Mr. Slater's letter on grain as possible, but it is sometimes very difficult to draughts with which he says he was at one time very keep a little "chaff "from going in with it. With much puzzled-that is, where a "given time" is men- respect to the letter of Mutual Improvement," the tioned as having to be taken into account when finding substance of it is just what I am anxiously waiting for the draught between any set of rollers. Time is an myself. Will E. Slater, before he takes up any other element that need not be introduced into the calcula- subject, kindly give his attention to the following tion at all, as it would only make it more complicated. queries, and let us have them in a plain, simple manThe draught is simply, as I have stated before (p. 136), ner. What does he mean by saying he did not expect "the ratio between the surface speeds of the first, or Factory Lad" to have so many replies to his questaking in roller, and the last or delivering roller," and tion, and yet to give him a rule which, if correct, not this ratio can be found without the trouble of finding one of the hundreds of subscribers can understand, their respecting speeds for any "given time." By even now he has given two explanations? 2. Does putting the speed of the first roller as equal to 1, he mean in his statement of successful spinners that multiplying and dividing by the figures representing they succeed in spite of the evil of draw-boxes," the various wheels and rollers, we get a proportional koiring them to be an evil? 3. Why is a bobbin when speed for the delivering roller, which is the draught leading more equally pressed than when the flyer leads? between the rollers. As an example, take the figures 4. Will he kindly allow me to see his Jack frames ... and the bobbins leading? 5. Can he run them 130 per min. and put turn per in. in his roving-or rather slubbing-with the bobbin leading? Lastly, will he explain what he means by putting the cart before the horse, if I intend it to go?" (No chaff.) The above queries, answered in a clear, definite manner, will please his brother subscribers, be satisfactory to our worthy editor, and will greatly oblige. THE HARMONIOUS COTTON SPINNER. MR. BEARDSLEY'S TRUTH AND TEMPER. readers were all so "flat" as to believe that you SIR, Did you realy concieve it possible that your "believed in free discussion" when you said so in your remarks on page 210 ? It realy is of no use trying to convince a staff -bound editor, so I do not attempt it further; but I will just remind you that the reason why I did not send you my fifth letter last week in the usual course was that I saw plainly that fair play in connection with the ENGLISH MECHANIC was out of the question, and I therefore did not think it worth postage. You know you have been guilty of the grossest partiality, and as such is the case I beg to tell you plainly your conduct shows you neither encourage "free discussion " nor do you appear to have any desire to keep your promises," and as a matter of Course "redeem them." But you can inform your intimate friend Proctor (B. A. and I do not know what besides) that if there is "Other Worlds than Ours," there is also other printing presses than that which turns out the ENGLISH MECHANIC. I now take leave of yourself and that trio of sophists you priviledge, by subscribing myself a disgusted subscriber, but a later of humbug, J. BEARDSLEY, Langley Mills, Nottingham. [If Mr. Beardsley has lost the truth, he might have endeavoured to keep his temper. His reason for not sending his fifth letter is not the true one. He did not send it because we did not insert his fourth letter, which we received about three weeks before; and the reason we did not insert it was that everybody, with insertion of such letters was an utter waste of space, the exception of Mr. Beardsley, considered that the Mr. Beardsley's reason for not sending his "fifth" letter is of the same character and quality as his reasons for the earth being a plane and not a globe. We never promised him unlimited space for the ventilation of his childish theories, and he ought to be obliged to us for the indulgence we have shown him. He may abuse us to his heart's content, as it will neither ruffle our feelings nor disturb our decision.-ED. E. M.] [We print Mr. Beardsley's letter rechatim et literatum.] GEOLOGY. SIR,-As Mr. Proctor has now concluded his so ably written papers on" The Earth, its Figure aud Motion"; I should be most happy, with your consent, to write a series of articles on The World, its Formation and the elements of physical geology to those of my fellowAntiquity," in which I would endeavour to impart subscribers who may be as yet unacquainted with them. I will not here enlarge on the beauty, or the utility, or the interesting nature of this science; let it suffice to say, that it is the most practical, rext to chemistry, and the most beautiful and sublime, next to astronomy, of all the classes of natural knowledge. I think that these recommendations alone, entitle it to have its leading principles more generally known than they are, and, Sir, I know of no more certain means of arriving at that desideratum than through the pages of the journal of which your are, without flattery, the head in every sense of the term. It may seem presumptuous on my part to take upon myself to teach this branch of science, when the other branches are represented in your pages by men so much superior to me, both as writers, and teachers; but believe me it is merely in the absence of someone else, that I offer my poor pen for the service, conscious, however, that it will shine but feebly in comparison with those of "our" astronomical, and other authors. ARTHUR UNDerhill. [We most cheerfully afford Mr. Underhill space for his letters, and particularly at the present season, when what we may term out-door scientific pursuits may be so advantageously followed.-Ed. E.M.] ANGLES AND TANGENTS. SIR,-In reading over the pages of the ENGLISH MECHANIC of the 10th June, 1870, I noticed on page 85,"Hugo's" assertion, without proof, that "angles are not proportional to their tangents." May I beg to ask him is an angle, or corner, at the centre of a circle, the measure of an are of that circle? and is the tangent an arc of that circle? If the lesser leg of a right-angled triangle be divided by the other leg of that triangle, the quotient in every case will be the tangent of an arc or angle opposite the lesser leg, as in the following case, by logarithms-viz. :— 7-968689 unity:: 35972629: 5-6285739" tangent. And in every case where the given terms have the same ratio as the foregoing we will have the same result, as, 7·968689: 7410648466: : 1·50103944 0·9429990. = 8.769988", as in the other case. And in every case the sine of any angle is to unity as the cosine of the same angle is to the tangent of that angle. VERITAS. THE PHANTOM" WHEEL. SIR,-A writer who signs his true name cannot be called upon to reply to anonymous critics, as such writers may possibly be presumed to be either ashamed or afraid to put their real names to their letters. As Mr. J. A. Mays, however (page 255), has signed his last communication to the ENGLISH MECHANIC on the subject of my velocifere," I will beg the favour of a small space for the explanation. Mr. Mays is perfectly justified in upholding the views of the Phantom " Co., but I should very much wish to know the reason why that gentleman has selected my velocifere for animadversion out of hundreds that appear so frequently in yours and other journals, in all of which high speed is impracticable, for at 10 miles an honr only the legs of the driver would have to make 90 double strokes per minute. Mr. Mays seem to have a jealousy in regard to speed, but he must himself know that on smooth reads, and all roads are smooth with deep rubber tires, speed can only be limited by the resistance of the atmosphere, very great at high velocities, or by the amount of danger in meeting with obstacles. Rubber tires are easily affixed to wheels of any description, and the vulcanised india-rubber rings may be obtained of the proper dimensions and thickness, ready to be put on, at any of the rubber manufactories in town or country. Rubber tires were proved at the Great Exhibition of 1851, when a heavy cart wheel so tired was allowed to run over the toes of the bystanders without causing the slightest sensation of pain. I have no pecuniary interest whatever in the matter, as my velocifere is not secured by patent rights, to which I have a most decided objection. The patent laws as they now stand form a lottery from which 99 out of a 100 applicants derive a loss instead of a prize, neither have I any faith in any possible improvements being carried out, for the public is the only judge of the value of an invention, and no committee, or jury of scientific men can forestall, or anticipate that judgment. I need scarcely allude to the disagreeable concomitants of even a successful patent-piracy plagiarism, riders, men of straw, and of expensive law suits, the costs of which must be drawn from the pockets of the great mass of the public, the consumer. HENRY W. REVELEY, Reading. STEAM LIFEBOAT. SIR,-Allow me space in your valuable columns for a reply to the objections to the adoption of my improved self-righting steam lifeboat enumerated in the letter of Mr. Richard Lewis, which appeared in your number of the 27th ult. I have fully considered and provided for the necessary requirements, for which purpose I will take the objections in Mr. Lewis's letter seriatim : "1st. That owing to the large quantity of water which must break over lifeboats in heavy surfs, amounting often to three or four tons weight, it would be difficult to keep the fires from being put out, and at the same time provide sufficient ventilation." To prevent the extinction of the fires, I provide the funnels and air-shafts with a cowl of peculiar construction, which, whilst permitting of free draught for the fires, and perfect ventilation, prevents any influx of water by the breakage of a heavy surf over the boat. Nor can these cowls be carried away by the wind, or when struck by the sea, or capsizing of the boat. The second objection made is, that "the motion of boats under such circumstances is so great and violent that they sometimes stand almost perpendicular, with either the bow or stern uppermost; that the propellers would work at great disadvantage, and the machinery would perhaps be liable to disarrangement." I obviate this objection by providing a screw propeller both at the stem and stern of the vessel. These propellers being mounted on the same shaft, will always work in unison; and as one at least will always be submerged, there is no fear of the engines "racing." I dispose and secure the boilers and machinery at the bottom of the vessel in such manner that the engines, &c., could not by any possibility become displaced or disarranged by the motion of the 3rd. "That the space occupied by the engine, &c., would make it impossible to use oars if the former should become disabled whilst afloat," &c. boat. Not only do I leave room to man the usual number of oars without increasing any of the dimensions of the vessel, but by merely adding one foot to the ordinary length I am enabled to man 12 oars, instead of 10, as usual. Moreover, should the engines be disabled from any cause, the propellers can be immediately unshipped and the vessel propelled by sails or oars alone. 4th. "That such boats would require to have a qualified engineer (engine driver) to keep the machinery in order and work it when afloat," This I do not consider an objection to my invention, as I am convinced that the increased expense attendant on increased efficiency in the means of saving life and property will be amply defrayed by the benevolent public, who have already done so much to further that object. &C. 5th. That "some time would be lost in lighting the fires and getting up steam." By the use of oil as fuel, steam may be got up in from 10 to 15 minutes, even while the boat is being carried down to the beach and prepared for launching; so that no time would be lost. Indeed, my boat could set off, if necessary, with three or four only of her crew, whereas ordinary lifeboats are frequently detained, for want of hands, when every moment is of vital importance. C. W. PETERSEN, Master Mariner. STEAM CARRIAGE. SIR,-I enclose a photograph of a steam-carriage that has run 1000 miles at the cost of 1d. per mile, one farthing per mile for each person. It has run 62 carrying four persons, coal, oil, and toll-gates, making miles in 7 hours-that is, from Birmingham to Glou Its think it provable that steam power can be advan-ful for its bass, as Sam Weller would say, "I should cester, ascending and descending some of the steepest ON THE PIANO. G. PREW, SIR,-I am sorry that severe pressure of business has prevented me hitherto in forwarding my promised communications on the piano. Pray accept the miserable excuse of "better late than never," the more especially as my esteemed friend the "Harmonious Blacksmith" has deputed me to reply to several questions addressed to him in the ENGLISH MECHANIC as being more acquainted, as he is pleased to term it, with practical details than himself, an assertion he cannot prevent me questioning. If instead of trying to do what every pianoforte maker who understands his business can do easily, my friend the "Harmonious Blacksmith" and some of my fellow-readers who are more practical in their crotchets than he is, would exert their ingenuity to increase the power and purity of the treble, I should have no need to ask cui bono? It has been attempted, but I have seen none yet decidedly successful. One method is to enlarge the sound-board beyond the bridge; but this in the two specimens I saw, though most elaborate in every respect, resulted in failure. Extending the sound-board within the bridge seems more promising. Erom the time of Dodd, Goodwin, Nosworthy, and A. Wornum, to the late design of Steward we have had repeated attempts to carry out the idea; but I have yet to see it carried out successfully so far as increasing the power of the treble is concerned. My present subject is on the improvement of the basses and trebles of pianofortes. A German harpsichord maker put additional bass strings to his instruments, which were sounded by pedal keys; and one of Handel's favourite "concert" harpsichords had this alleged improvement. At a later date a Scotch pianoforte maker used very thick brass and copper strings in a similar way in his grand pianofortes. More recently attempts to reinforce the bass have been made by enlarging the sound boards, as carried out by Gedwin in 1836, and others, including my friend the Harmonious Blacksmith," (see his rather costly design for an upright grand cottage piano in No. 235); and yet more recently by Mr. Steward, who extends the sounding board to the left of the bass strings at the cost of rendering the instrument yet more unwieldy. In addition, separate pedal pianos have been made by Woolfe, see his patent of 1858, No. 1081; and we are soon to have a public performance of Bach's pedal fugues by a celebrated French pianist on one of these instruments, which, so long as its use is confined to such music, may be pleasing, but hardly so effective as organ performance. If used to give breadth to the bass of legitimate pianoforte music, it is not only not needed, but is less suitable for accompaniment than Another and more promising mode of increasing the bass of a good piano of the ordinary construction, power in the treble is doing there what the independent nsually quite powerful enough without even addi-pedalier does for the bass, viz., using two pianos intional surface of sound-board. Witness any of Broad- stead of one, in the same case, the whole of the strings 6th. That "it would be difficult to apply the self-wood's magnificent concert grands. So I think I am of the said (literally) two pianos being actuated by righting property to such boats; and if they were to justified in asking the designers of the so-called im- one actian or mechanism, In No. 208 "J. J." proposes remain more than momentarily keel up, the fires would provements, cui bono? this plan, and in No. 278 the "Harmonious Blackbe put out, or they might set the boat on fire." I provide air chambers of my improved construction tical character than many of his crotchets for carrying smith" has offered some suggestions of a more pracabove the deck, which ensure the righting of the boat: it out. "J. J.'s" design is not intended to increase and as the machinery is disposed entirely at the bottom the loudness of the sounds uttered by any given string of the vessel, it must increase the self-righting proin the treble; but it really is what I have before perty of the boat. The funnels and air-shafts are prostated it to be, viz., two treble pianos in one case. vided with self-closing caps, which prevent any influx It is true, there is but one sounding-board common to of water whon the boat capsizes, whilst the boat may both, but each string or set of strings has its separate be built of, or lined with, metal, to avoid all chance of pair of bridges, although one bridge of each pair is on the same sounding-board, and each of the other 7th. That "the cases of failure of the present lifeboats are so rare, that the committee of the Institution pair is on the same intermediate metal bar. Each string also has its own hammer, though they are both have not felt called upon to expend large sums of on one shank, and move on one centre.,, I feel, theremoney on experiments which might not afterwards be fore, quite justified in terming J. J.'s" design two attended with beneficial results." I need hardly refer to the award of £100 made to treble pianos placed above each other in one case. We all know, two pianoes, sounded together, are louder me to show that the Committee of the Royal National Lifeboat Institution are fully satisfied of the benefits likely to result from the introduction of my improved steam lifeboat, whilst a reference to the Shipping and Mercantile Gazette will show that the present service is not by any means efficient in all cases. 8th. That "wherever steam tugs are available, I its being set on fire. piano, and I can testify to their great utility for the As it is far easier to make a piano whose bass over- than one. The chief objections to this plan are the difficulties of construction (perhaps the "Harmonious Blacksmith's" design for carrying it out might be cheapened and simplified): also the unavoidable increased height of the instrument. To me personally this latter is no nt I much prefer a six feet cabinet to: objection at all. four feet cottage; but commercially it don't pay to make pianes than 4ft. 4in. more at the most. People don't know what is good for them, and won't buy tall instruments with plenty length o string for producing basses of fine quality. If "J J.'s." planjwere carried out as far down as the compass as pitch C, it would add something like two feet to the height, thus making a four feet cottage as tall as a four feet cabinet. I fear only the few who prefer music to furniture would become purchasers. I fancy that the difficulty of tuning such an instrument would be considerable, and I know from experience that the majority of pianoforte tuners are neither careful nor intelligent enough to tune either this or any other instrument requiring unusual care or intelligence. The pitches of the upper and lower strings must be altered, but very little at one time, or a large proportion of the whole tensile force of the strings would be resolved on the intermediate metal bar which carries the two bridges. To avoid this evil will require an amount of care and caution that tuners who are accustomed to "pull up" strings a whole tone or more at once can hardly be expected to exercise-but perhaps, like the Tory party, they might be "educated." Some difficulty might be experienced in adjusting the upper hammers to strike their strings at the same instant, and with the same force, that the lower hammers strike their strings, but it can be done if the workman's head is screwed on the right way. No one who works only by the rule of thumb" should be entrusted to do it. I know I could do it myself; indeed, after more than thirty years practical and extensive experience-not to mention the many, many long months I have been engaged during my spare hours in carrying out no end of what I may term the "curiosities" of pianoforte making, for my friend the "Harmonious Blacksmith," there is literally nothing I should be afraid to undertake. If originality of idea (unfound in the Patent Office records), occasionally even to me appearing to verge into absurdity-utter disregard for the ordinary usages and practices of the trade, which has caused many a wrangle between us, and his persistent determination, to test to the very last, the pros and cons of his ideas at any cost, cannot fail to give a man experience in his trade, I ought to confess to myself under deep obligations to him. I have not only learned more theoretically from him, a mere amateur, than any man in the trade could have taught me, except I had access to the knowledge locked up in the archives of such firms as Broadwood, Collard, and Erard, which only oozes out by driblets in their productions; even then it is only visible to those with brains to appreciate-but I have learned in the pleasantest possible way-viz., by being well paid for my time. We must all pay for our fads, and he is no exception to the rule that "Children must be paid for." In my next, with your permission, I will reply to a few questious by "Harmonious Blacksmith's" desire, though addressed to him. W. T., Pianoforte Tuner and Repairer. ROBERTS' GALVANIC BATTERY. SIR,-It gave me pleasure to read in your ENGLISH MECHANIC for 27th April, page 141, the testimony borne by Mr. H. Chapman to the great advantages of the galvanic battery which I invented in 1852. Permit me to say that the cost of the battery (which he properly states is great when platinum is used as a negative plate) is reduced fourfold by substituting graphite for platinum, and the battery is not much diminished in power by such change. I have used my battery for electric light, and for fusing iridium many successive hours with undiminished force. I used long drain pipes (stopped at bottom) to contain the exciting liquid. These pipes were about 36in. long. The plates being Din., were hung at the top thus, 1, 1, graphite, or platinum; 2, the zinc plates. The vessel was then filled with dilute nitric acid, sp. gr. 1240. The action is as follows: Part of the oxygen of the acid combines with the tin, forming metastannic acid, which, being comparatively insoluble, falls away from the surface of the tin plate to the bottom of the deep vessel. The surface of the plate is thus kept clean, and the exciting liquid is not encumbered with any opposing metallic solution (an evil in all other batteries). Further, the metastannic acid falls down as a hydrate thus carrying with it an equivalent of water, which tends to maintain the supernatent liquid nearly at its full strength, Again, the product of the battery, after obtaining the elec tric force, is a marketable commodity, metastannic acid being used in calico works. We sent more than a ton weight of this product of the battery to Manchester, and sold it at a price which paid nearly for the cost of working the battery But the competition by Young's process of making metastannic acid direct from the ores of tin kept the price down, otherwise we should have had our electric power for nothing. I would venture to observe that this is the end to which experimenters in electricity should direct their attention viz., to make the product of the battery pay for the plates and exciting fluid. As the nitric acid gave up part of its oxygen only to the tin, nitrous acid fumes were given off abundantly; but these fumes were collected into a peculiar kind of reservoir, in which they were condensed, and part of the acid thus recovered. Circumstances directed my attention to other matters, and I have not followed out this matter as I ought to have done. I cannot refrain from bearing testimony to the exceeding usefulness of your publication and the excellent spirit in which it is conducted. MARTYN ROBERTS, Pendarrow House, near Crickhowell. MECHANICAL FINGERS. SIR,-1 have just invented a very useful mechanical contrivance, a photo of which I enclose. Three weeks ago, I had a machinist apply for an arm amputated a few inches from the shoulder, and she wanted amongst a number of appliances, an instrument that would hold the work like the natural fingers, to enable her to hem, stitch, and tack her work for the machine, After many trials I succeeded, and so successful is the appliance, and simple, that in a short time she was enabled to stitch and hold the finest or coarsest fabric, with almost as much ease as with the natural fingers. The instrument is fixed in the wrist, and is removed, as you see, instantly on touching the spring. There are three rods corresponding to the thumb and the first and second finger; the two under rods are fixed; the top one, over which the work is drawn, is movable in any direction, and bound to the other two by a vulcanised rubber band; this band according to its tension keeps the work. On to each rod is a piece of brass tube, which revolves when the work is drawn. Over the two under tubes is slid a piece of vulcanised rubber pipe, The work is placed in the instrument precisely as it is in over the index finger, the vulcanised rubber holds the work just like the soft cushions of the fingers; as the person stitches she can draw the work, the rollers revolve, and thus they can hem, and stitch at any length. Ladies who have lost an arm at the shoulder, above or below elbow, may now by the use of this instrument follow their favourite employment, which through their loss they may have long been deprived of J. GILLINGHAM. THE AIR PUMP.-THE HIGHEST VACUUM. SIR,-A common exhausting syringe will produce a vacuum sufficient for the experiments mentioned by "Inductorium." p. 252, but at the expense of much labour. Certainly "Inductorium's " air-pump should do the work well. If, however, he requires stratification, the case is very different. I have never been able to produce it with a double-barrelled pump, but a small pump which I have, on Yates' plan, gives me very good results. The form is shown in sketch, omitting unnecessary details. There are valves at A and Al opening out wards, but none between the barrel and the receiver to be exhausted, so that the rarefied air has no work to do in lifting valves. The pump is hard to work at first, but beomes easy as the exhausWere tion proceeds. Inductorium "1 not so well acquainted with the subject, I should suppose that the joints of his apparatus were not air-tight, but that, I suppose, is impossible, and therefore I can not account for his failure. If "Inductorium " will furnish details of his coil giving 4in. sparks with a single small cell, and having only 4in. of secondary, he will much oblige. SALADS. J. V. SIR,-On page 159 of our MECHANIC, "Beta" appears strongly to advocate the use of dandelion as a salad. But he forgets to consider that mankind in general do not relish the taste of this herb as a salad, and hence it is rejected by almost everybody, at least in this country, nor will any commendations of its good qualities, which it assuredly possesses, induce people to use it, knowing, as they well do, that there are other herbs as good, and even superior when used as salads. Dandelion is most effective in diseases of the liver. It may, in fact, be considered, particularly the roots of the herb, as almost a panacea for ailments of that organ. On the kidneys, too, it acts beneficially, and no doubt on the spleen as well. But dandelion as a salad is most unpalatable, and even when blanched it is anything but agreeable. I have tried all kinds of salads, and there is nothing, in my opinion, to excel our old friend watercress. It is always welcome, and always wholesome, and can scarcely be sufficiently praised. We ought to eat a good deal more of it than we do. It seems to be universally liked, and, like plantain, seems to follow man wherever he goes; I have seen it growing profusely near the Falls of Niagara, and I believe in the neighbourhood of Montreal and other places. In "Beta's " list of salads, I observe the word beer," this, of course, is a misprint, and should read "beet." I am rather surprised that this gentleman has not included mustard in his list, for it is well liked and largely eaten mixed with cress, nor has he mentioned young onions, which are much consumed in the spring time of the year. I may add that the leaves of Indian cress (the common nasturtium), fare a good salad. They are not as hot as horse radish nor as cool as a cucumber, but agreeably piquant, and far preferable, I think, to dandelion leaves. On the Continent this cress is, one may say, in general use, but here in England we do not seem to care about it as a salad, and only admire it for its gay and variegated flower, and for the great ease with which it is grown. I cannot agree with "Beta" in his remark that through ignorance or prejudice many of the salads mentioned by him are at present despised by mankind. They are not despised, but simply unused, mankind having discovered other salads more a reeable to their tastes. ORTHOTOPTICS. TAUTAU. SIR,-Your esteemed correspondent "The Welsh Shepherd," at page 257 calls attention to a subject which has been frequently discussed among physiologists-namely, the rectitude or inversion of vision. Now, to begin. We are perfectly acquainted with the anatomy and mechanism of the organs which subserve that sense, and we know that, in contradistinction to all our other senses, a perfect fixture, though very small, and inverted, is actually produced on a convenient part of each of these organs. But there our knowledge ceases to assist us as to the effect produced upon the so-called sensorium, and this, in all likelihood, will remain a mystery so long as we are in the flesh. As for conjecture, there has been plenty of that, but none of it can be of much utility. If I understand the "W. S.'s" communication rightly, the gist of his argument is that monocular vision would present objects in an inverted position to the mind, while binocular vision would produce the sensation of erection. In other words, that two upside downs are equivalent to one right-side-upwards. In attempting to show this, he adduces the case of a little boy who was afflicted with disease, and perhaps congenital deficiency. But this case unfortunately, proves too much; for it is said that, in drawing the picture of a house, for instance, he drew it wrong side upwards; but then, if he had done that, his delineation, like everything else, would also have been inverted to him, and, consequently, seemed to him what would be right side upwards to us, and so, wrong side upwards to him. It would appear, then, that he was merely endeavouring to hoax the bystanders. This would seem the more probable, for we are assured that "the very rudiments sons for supplying the air from above, and I, for one, effect? Mr. Reveley, however, probably has good rearespecting his novel plan. He also refers to the benewould be most happy to have further information fits arising from the carrying off of the products of gas combustion by means independent of the general ventilation. A proof of what may be easily effected in this having rather a low ceiling, was fitted up with gas, but way lately came under my observation. An old house. the air always became very oppressive when the gas had a tinned iron funnel constructed, some 10 or 12in. was burning. The occupant being an ingenious man, diameter, and suspended over the burner; the funnel terminated in a tube about an inch in diameter, through which all the products of gas were carried into the house fine. After the adoption of this plan the air in the room remained cool and fresh. -be optic nerve on the left side ere wanting." w, if this description be accurate, it would imply a y extensive deficiency of the brain, reaching back far as to what is called the external genicular body, and tid excite no wonder at a perversion of intellect, or the malformation would probably not be confined that tract. The aspect of a fungous growth at the attom of the eye is not crystalline, but metallic, and as well described some time ago in your columns by Ussher, whose good-tempered articles we have rently missed. It is easy for any body to try whether nocular vision inverts the impression on the senium by simply closing one eye, or, if that will not fy the "Welsh Shepherd," we have no end of case most extensive lesions of the brain on one side His theory about the decussation of ly to aid us. ve fibres in the optic commissure will not hold ter for one instant, the fact being that the crossing rely produces a distribution of right hand fibres to right hand side of both eyes, and rice versa, thus -uring a consentaneous action of the two sides. We ve a most remarkable case on record bearing on is subject narrated by Locke, I think, in his essay <n the Human Understanding." The question was Opounded to him by the celebrated Mr. Boyle, hether, supposing a person to be born blind and to ave his sight afterwards given to him, he would, by aere inspection, be able to distinguish a cube from a here. Locke, after some reflection, replied that he ould not, and shortly afterwards an opportunity resented itself of testing this, for one of our great rgeons, Mr. Cheselden, encountered a young man 21 Cars of age, who was born blind, and remained so, aving congenital cataract. Mr. Cheselden operated him, and he recoverrd his sight. He was not able to 11 a cube from a sphere without manipulation; he After a period a w objects in their upright position, but everything appeared painfully close to his eyes. esaw like other people. There are, then, no means of ascertaining in what position we see objects, or, indeed, if we all see them nlike manner, because their relative positions and magnitudes are similar in all cases; it does not, howver, follow that because the picture is inverted at the fundus of the eye, it should be so carried to the norium, for it may be there presented horizontally with the base forward, and if so there would be a olution of the question. But we are not to suppose that people always know hether they are looking at an object right or wrong ide upwards, for if we go to the palace at Hampton Court, we shall find the visitors looking at the picures on the ceilings from all parts of the 100ms. ew may be aware of it, but such, notwithstanding, is The fact, that the large majority of persons contract a abit of using but one eye, to the detriment of the ther, so that the unused eye loses, partly or entirely, the faculty of focussing and adapting itself to see at <ifferent distances; and this may be perceived if we 1ake a book and attempt to read first with one eye alone, then with the other, also alone. This should be attended to by those who have to wear spectacles, as We cannot, as just i frequently happens that glasses of different focuses are required for the two eyes. observed, tell how others see, as we have no means of instituting a comparison, and, for aught we know, one persou may see as though he looked through the small end of an opera glass, and another as through the large end. The impressions produced by colours may also be widely different. To conclude,-it is of little consequence to us whether objects are presented to us upright or inverted, as all know who are in the habit of using the microscope, for here the bottom appears to be the top, and the right hand size the left, and vice versa, but our experience soon enables us to supply the correction. F.R.C.S. In am PECULIARITY IN EYESIGHT. SIR-For about two years my eyesight has been failing me out of doors (to correct which I use conFor reading it is as good as ever. cave glasses). looking at, say, a flagstaff with the left eye, favoured with three images thereof-namely, the flagand an image parallel thereto like a shastaff proper, With the right eye, and with both dow at each side. eyes at once, there is only one shadow-to the right. In looking at a pretty girl this peculiarity is agreeable enough (my wife here pulled my ears), but it detracts very much from the appearance of a landscape, &c. I suppose it is caused through the irregular flattening of the eye lens through natural decay, perhaps accelerated by following my daily avocation in a too glaring light. I have a window in front or me and one to my left. Thus, my work is in the light, while the light also falls upon my eyes. Now, it seems to me that this disposition of the light will cause the pupils to contract irregularly, and that the centre will flatten by age and use; but that the outer edge (irregularly protected) What will be preserved in its original convexity, thus causing two or more foci in the same eye. strengthens me in this opinion is, that at dusk, while other people can see easily, everything is a blur to me, and when it becomes dark, by the greater dilation of the pupils, the focus of the outer edge becomes the principal one, and so I can see tolerably well again. Should any of my brother readers confirm me in this opinion, I will take steps to remove the cause. pinion will oblige. BLACKBURN AMATEUR. J. HASTINGS. SIR,-To continue: (7.) (1) 7 10 - 13:= 87 3 = 11 (2) 10 y = 57 (8) 3 20 + 14 (4) 2 x 11: = 50 Multiply (1) and (3) by 3 and 7 respectively, subtracting products. 21 - 39 z = 261 21 + 93 x = 399 Multiply (4) by 49, adding to (5) (5) -98 x 98 x 39 z = 539 % - 138 2450 acy + ab=a2 Add to this (1) multiplied by c (4) bcx+acy = b2 - az (11.) - 22 b cx ac y = c2 -7x= (c) √ 2x = 7 x - 52 52)2 2x = (7x 49 x2 + 730 x = 2701 2704 730 x = 49 x2 - 728 x + 2701 12 S730 + 49 98 49 VENTILATION OF BUILDINGS. SIR,-I have read with much interest Mr. Henry W. Reveley's letter (No. 269) on the ventilation of buildings. Seeing that the enjoyment of health so much depends on the proper supply of pure air, especially to Welling-houses, the importance of this subject cannot, Mr. Reveley's plan is to I think, be over-estimated. *upply the fresh air from above, through the ceiling, and expel the bad air through the floor. Would it not be better to reverse this plan, and supply the pure air from beneath, while the impure was expelled from above, seeing that the heat and breath of the body and the products of combustion have all a tendency to -read-at least there exists a general belief to that 2016 9504 SIR,-I observe a correspondent, H. W. Bishop, (4004), asks that another series of articles shall be given upon spectrum analysis. Allow me to support this suggestion, and add that no doubt there are many who like myself possess a small laboratory for experimental chemical investigation, and who would be glad to adi to their stock a spectroscopic apparatus if it could be provided at a not too great cost. My own case is this:-I have a good practical knowledge of analytical work, and desire to acquire an equally practical knowledge of spectrum analysis. At present I know little more than the name, and to inake my laboratory more complete and useful, to add a spectroscope for chemical purposes. Therefore any information conveyed through your columns to assist in either making, arranging, or where to purchase and work the necessary apparatus, will be duly appreciated. TRADE AND COMMERCE. W. R. SIR,-The second paragraph of "F., W. M.s" letter on page 257, expresses a very common belief, but one so pernicious, that the error caunot be expressed too often. He thinks that we ought to refuse to buy cheap goods from the foreigner if he refuses to buy cheap goods from us," because if we did so buy them we should be paying the wages of the foreign workman who made them, and therefore there would be just so much less (money) for our own workmen," who are thesefore compelled to emigrate. "It is pretty plain that for each foreign workman we support in this manner, one English workman is compelled to leave his country or to become a pauper." As all this is heresy of the blackest hue in the eyes of all orthodox true believers in political economy, I thought I might safely leave this portion of “F.W.M.'s" letter to other and more competent writers; and therefore confined myself last week to vindicating my first letter, which "F. W. M." somewhat cruelly held up to ridicule. Having a most salutary horror of encroaching on your space I intend to state principles without any of the qualifications they require in practice. I will start with two axioms. 1 A conntry that imports goods, pays for them by its own exported products. 2. Wages are paid out of the accumulated wealth of a country. In these questions one part of the transaction is obvious, the other, the compensating one, requires some attention to find out. When I buy a foreign-made article, "F. W. M." even sees, that part of the money I pay for it, goes to support the foreign workman who made it. What he does not see is, that some foreign gentleman pays an equivalent sum for some English article that strikes his fancy, and that part of his money goes to support an English workmen, for taking the whole of one nation's trade with another, the one transaction cannot happen unless the other happens too. Therefore, when we have got only thus far, we find that the English workman is equally supported whether I buy a British or a foreign inade article. Let us now go one step further. If I buy a foreign article in preference to au English one, it must be, because it is, cæteris paribus, cheaper than the English one. Let us suppose, for instance, that I get for 10 a foreign article; whereas if I bought a similar English one I should have to pay £20 for it. No one can deny that I am £10 richer for my intelligent preference, and have that extra £10 to lay out on another article; for no sane person now puts away his savings in an old stocking, he invests it somehow or other, therefore, I shall still lay out £20, on industrial products-English or foreign makes no difference to the English workinan, as we have found above. The result is that I am richer by £10 for choosing the foreign product; that is to say, that the fund from which wages are paid is increased by that sum; which, in the long run is god for the working classes; ergo, buying a dear English product when you can get a foreign one as good for less money is a dead loss to the community. HERBERT. DESIGNS FOR THE LATHE. SIR,-In your very interesting paper I have noticed some letters inquiring about the best mode of trying and recording designs executed in the lathe. The common method of doing this, by a paper on the chuck and a pencil in the slide rest, is at best so very inconvenient and unsuccessful, that many amateur turners among your readers will doubtless be glad to learn a much superior proof. That you may be able to judge of the result obtained. I enclose a couple of samples; and these are selected on account of their imperfections, that you may see what are the difficulties to avoid, The card is common enamelled or ivory faced cardboard, such as may be bought in sheets of any card maker, and cut to fit the chuck. This cardboard, after being cut, is brushed over with Indian ink, two or more coats in opposite directions, until a jet black surface is obtained. This must be done quickly, with a light hand, so as not to soak up the enamel and the ink must be good and rubbed smooth, free from lumps, as the least knot on the paper injures the design. These cards are held upon any flat chuck by a narrow brass rim; the rim is fastened down by a catch on each side of the chuck. flat. The tool is a needle-point, which is pressed forward by a spring; its penetration is regulated by an adjustable shield, as the card will never lie perfectly The lines, being white upon a black ground, will be distinctly visible however fine they may be drawn ; and there is scarcely a limit to the delicacy of the work which may be executed in this way. The cards may be easily preserved, and the sittings" noted upon the back of each for future reference. If the designs are wanted for publication, any photographer can copy them, enlarged or diminished, if required; and they are much more effective than the patterns printed from blocks, on account of the greater distinctness and delicacy of the lines. Should any of your readers who are turners desire it, I will send a drawing of my tool; I do not now do so because I am not a good draughtsman, and am, moreover, not certain of the favourable reception of my suggestion. Still I wished to share with my fellow amateurs an invention which has given me much amusement and much pleasure to many friends. V., New York. [The specimens enclosed by our New York correspondent are exquisitely executed. We should be glad to give, for the benefit of our readers, an illustrated description of his lathe.-[Ed. E.M.] good recommendation; but if, in addition to this, the FOCAL LENGTH OF CONCAVE LENS. SIR-It may perhaps interest "A Fellow of the Royal Astronomical Society," page 251, and his querist Scorpio," to know that on page 19 of "Smith's Optics," there is given a method of finding the focal length of a concave lens by experiment. It consists in covering the lens with a piece of paper, in which a few pin holes have been made. The focal length may then be discovered by holding the lens in the sun's rays at such a distance before a sheet of paper that the distance of any two holes on the sheet of paper may be double the distance from each other of the two correspondig holes in the paper on the lens. The distance of the lens from the sheet of paper will then be equal to its focal length. The experiment may be somewhat varied by placing a piece of cardboard with a single circular hole in it in contact with the lens and a sheet of paper on which a circle has been drawn of twice the diameter of this hole at such a distance behind it that the diffused circle of light from the less may just fill the circle. The distance from the lens to the paper is its focal length, as before. If the lens be ground on its edge, it may be sufficient simply to hold it before a sheet of paper on which t circle twice its diameter has been drawa. HENRY T VIVIAN A CUMBERLAND MINER'S APPEAL SIR,-Having witnessed a very serious accident today, by which a comrade has lost his eyesight for ever, I seek the assistance of my fellow-subscribers for the means to prevent such accidents. powder is blasted in the man's face. We have made the prickers of copper, but they do not answer, as we flatten them whilst stemming," and then we cannot About 5 miles from here, past the Sugar Loaf Mountain, lie the domains of the Earl of Powiscourt, and by the courtesy of his park keeper, Mr. Hopkins, we were permitted to view the Deer Park Falls by noonlight, a scene that will ever be photographed on our memory. We retrace our steps to Enniskerry, and find comfortable quarters and au obliging landlord at the Hotel Royale; then, again taking the road, past Lough Bray, we visit some genuine Irish cabins on the hill side, containing, as usual, the pig that pays the rent, all the poultry, very little crockery and furniture, and a great deal of peat smoke. One thing you are sure of, and that is a hearty welcome to share their meal, which chiefly consists of potatoes (cooked with the bone in them), and milk. A more generous people I never met with; they are ever ready to assist and wish you "God speed." But we travel on past the Reformatory of Glen Cree, containing about 700 inmates, under the paternal supervision of Father Fox, to Round Town, through Rathmines and Rathear, into Dublin, and what time we have we may spend protitably by visiting Phoenix Park, the Cathedral, and many interesting places in the old city. And now2nd. To those who have a fortnight's leisure. We take the excursion from Blackstone Station, Dublin, to Galway (all particulars of the Midland Great Western trains may be had by writing to the courteous traffic manager, Mr. Skipworth), a distance of 130 miles, passing en route Maynooth College, Mullingar, Ballanloe, and other interesting places. The old town of Galway is thoroughly Irish; the women are seen in droves, dressed in the old red cloaks, and without shoes and stockings, carrying fish and turf. Visiting Queen's College, the famous salinon fishery, and the curious colony called the Claddaugh, and the pretty suburban town of Salthill, we book ourselves as passengers by the steamer that plies daily between Galway and Cong, the fare 18. 6d., a distance of about 30 miles. This is a pleasant little trip on the fresh waters of Lough Corrib; numerous islandsfare dotted here and there, and feeding on the shore we saw flocks of cormorants. Passing the residence of Captain Blake, and several dilapidated and deserted nunneries, we reach Cong, and by the kind permission of Sir A. Guinness we are permitted to roam over the spacious domain. About 34 miles distant are ihe waters of Lough Mask, flowing into Lough Corrib through a subterranean passage formed in the limestone, which has sunk in many places, forming immense caves. The inhabitants of Cong light them up with straw whenever visited by strangers. From here we pass through Ma'am is of various lengths, ranging from Itf. to 4ft.; it is made In blasting iron ore we use a tool called a "pricker," it (past Lynch's Hotel, a most remarkable structure, the of in. best nail rod iron (horse shoe), and drawn to a front of the place being, as the Irish express it, all at point. The use of this tool is, that during the process the back; the front part facing the road certainly has neither door, window, nor sign, and it is only by pass-drawn it leaves a space in the "stemming" down to of charging it is kept in the hole so that when withing round that we discover signs of life), on to ClifThe the powder, into which we introduce the straw. den, from here to Kylemore, and through the pass, straws we use are corn straws dried and filled with visiting the castle of Mr. Henry, one of the benefactors of Ireland, especially in the west, through As all our work is by contract, we very fine powder. THE GERM THEORY." never use the patent gutta percha fuze, except in very Letterfract and Lenane, two charming places, from wet places, because we cannot afford it, The danger SIR.-Will you allow me to say that, while agreethere to Westport, spend two or three days here, of the "pricker" is that during the process of pulling ing with "J-Mo" in a great deal that he says, ascend Croagh Patrick and feast our eyes with the down among the powder it ignites, and, of course, the (p. 25), I cannot imagine that the "building" he speaks scenery around the Bay of Westport, then take the of would be of the slightest use in curing consumptrain and pass to Foxford, from here by road to tion. I do not think Prof. Tyndall is quite sure him-Ballina, a town numbering about 5000 souls; here we self what the molecules floating in air really are; for see the quaint old Irish style of travelling, the wife although when the stream of air was passed through riding bebind the husband on the same horse, and a red heat the molecules were destroyed," similar holding by the tail of the animal with one hand and phenomena occurred when a tin case containing boil- clasping her husband with the other, from here we ing water was held underneath; so the molecules take the public car and travel comfortably to Sligo, the may be organic or inorganic for all that has been extremity of our tour, and here you may pass several proved at present. days, as the neighbourhood is extremely interesting alike to the botanist, geologist, and the pleasureseeker. Trips are arranged on Lough Gill most days. We now leave Sligo and return by train through Bally-electrified, to read in the last number of your excellent SIR, I was not a little surprised, I may even say mole and Longford to Dublin, and thus ends an excursion through a district exceedingly beautiful, but thinly magazine an account of the so-called "discoveries" in frictional, or high tension electricity, purporting populated, capable of being far more extensively culto have been made by Mr. J. N. Hearder, F.C.S., of Apologizing for the length tivated than at present. of this letter, I shall be happy to answer further Plymouth, and exhibited under what he considers to be a new form of instrument, and terms the Electric Fulgurator. F. HARWOOD, 33, Newark-street, Leicester. Permit me to say that these very discoveries, in all their identity, and in the very means [We should be glad to insert other letters containing employed in their elucidation, were made by me threereliable information for tourists, and particularly and-twenty years ago, fact for fact, and almost letter for letter, and word for word! These discoveries to the Royal Society in 1847, and which was road formed the substance of a paper which I forwarded before that learned body at Somerset House, in January or February, 1813. The Literary Gazette, of that period, gives a report of the paper, and will furnish the exact date. See also Proceedings of the Royal Society for 1848. In May, June, and July of the same year I delivered a series of lectures at the Royal Polytechnic Institution, on "The Phenomena of Thunder Storms, and the Cause of Lightning," &c., and I exhibited the powerful effects of my discoveries by producing loud and dense flashes of concentrated lightning through an uninterrupted interval of air three feet in length. I use the word concentrated, as referring to quantity, which was here combined with a coated surface of upwards of 100 square feet, and intensity. I employed 12 immense Leyden jars, having rapidly charged to the utmost by the hydro-electric machine of the institution. The flashes were sometimes straight, but generally zigzag, or like a long lar curve from the earth, and they were so powerful line of WW's, slightly bent, in the form of an irreguthat any one of them was capable of destroying life. Each jar was insulated upon a stout varnished glass pillar, 3ft. high, and the series were connected together by a framework of levers, so that when charged, they could be suddenly thrown into striking posi ion, to determine the disruption of the fla-li. Singularly enough, two-and-twenty years afterwards, this self-same discovery and this self-same arrangement, even to the system of levers and the glass insuPERFORMANCE OF SPECULUM. lators, exactly 3ft. high, are brought forward as novelties by Mr. Hearder. I tried at the time, howSIR,-Your correspondent, "Optical Bricklayer," in ever, to carry the thing further, and make a far more soliciting my opinion on 75-16ths in. mirror, has, so far as I can judge, accom- proposed to the directors of the institution to produce, the performance of his imposing demonstration than that above named. plished a decided success. He does not, however, give by such a combination of jars in their large theatre, a the number of the MECHANIC in which the engraving flash of lightning through an uninterrupted interval referred to is to be found; but if the lines of letterpress of 12 or 20ft, of air, which I could easily have accomare smaller than the ordinary correspondence columns, plished, and without danger, but they were afraid of such would, at a distance of 100 yards, be a sufficiently the occurrence of some fatal accident, and for this severe test for any ordinary aperture. The rentebility reason alone my proposed demonstration was abauof such small type at the above distance is of itself adoned. In proof of the facts above stated, I refer to That persons living at high altitudes rarely if ever suffer from consumption I imagine arises from the air being "lighter" as well as purer. Thus the lungs would take deeper inspirations, and become fully inflated and, so to speak, aerated. In other words, because the pressure of the atmosphere is not so great on a high mountain it becomes necessary to obtain the requsite amount of oxygen to breathe more deeply, and to expand the chest more fully, and consequently the lungs. For myself, I do not believe tuberculous matter can exist in well-acrated lungs. J こ M-o says that "air of great tenuity (?) will not inquiries. about localities which more or less abound with beautiful scenery or objects of scientific interest. TOURISTS' TRIPS.-IRELAND. SIR,-The great number of inquiries resulting from my note on the "Midland and Western Districts of DRY PLATE PHOTOGRAPHY. Ireland" fully proves that a tour through that romantic SIR, I strongly recommend "Tannic Acid" to try part is not without great interest, but as I cannot the gum gallie process in preference to the tannin. answer all inquirers individually, I hope you will He will find it more certain and better in every again do me a favour by inserting the following rerespect. For full details I must refer him to the marks, &c., for the benefit of those numerous kind "Year Book of Photography for 1870," price 1s, as to friends who, by their letters, evince a great desire to give them here would require an unfair amount of visit the Irish. 1st. I. would address myself to those who have only a week at their disposal. A circular tour preservative, dissolve separately, gallic acid, grs.; space; but I can briefly state it thus:-To make the through the county Wicklow they would find very interesting. We take the train from Westland-row 5grs.; water, 2drelims. water, 6drehms.; and gum arabie, 20grs.; sugar candy, These are to be mixed and station, Dublin, for Kingstown, a sixpenny ride, and filtered just before use. The plate having been coated then proceed on foot through the pretty towns of with a suitable collodion, is excited and washed as Dalkey and Killiney, where having obtained permis- usual, ilooded with the preservative, and drained and sion to ascend a mount, formerly belonging to John dried. Mappas, Esq., we view a splendid pauorama of many It may be developed with pyrogallic acid, but Mr. Gordon recommends the following iron soluEquare miles in extent stretched out before us. A tion:-Gelatine, 1gr.; glacial acetic acid, 15 minims; little farther on lies Bray, with its celebrated promon-protosulph. iron, 20 to 30grs.; water, 1oz; a few drops tory stretching out into the sea, called the Head of of silver solution to be added before using. The expoBray. Here we must stay a day or two to visit the sure is about from four to six times longer than for "Seven Churches," the "Devil's Glen," and the wet plates. "Dorgle." The legends attaching to these places told by the carmen in their own vernacular, are droll in the extreme. This glen of the Dargle is the most beautiful spot in the country. The rugged and precipitous sides rise on either hand to the terrific height of 400 or 5 oft., and are covered with the most luxuriant vegetation, among which are several families of splendid ferns; at the bottom winds the stream from which it takes its name. The sublime scene and the music of the waters as they rush along over the rocky bed cast a spell over the lover of nature which enchains him to the spot; but we pass on through densely-wooded ravines, until we reach Euniskerry, where we must also stay a day or two to explore. D.EDALUS. withdraw them. As such accidents are of almost daily occurrence, it would be a blessing to us poor miners could there be something invented to protect us. A CUMBERLAND MINER. ELECTRICAL DISCOVERIES. I |