87 4th vii 30 28 June W June 16 Sh263 19.0 Scale of 15' 30' 5/2 B48 $5 8B246 200 7 72 15 June From photometrical of the minor planets. determinations, Stone made the diameter 214 The magnitudes are expressed in E's Vesta. Vesta is usually considered to be the largest miles, Argeländer 270, and Pickering 319 miles. By direct measurements of the disc, Schroeter obtained a diameter of 333 miles, Mädler 300, 16 180: 25 ± Tacchini (at the very favourable opposition of 1880, 9.5: 312 : 48.3 when he used a power of 1,000 on the 10in. re9.5 115 8.0: 292.6 2.1 reddish, blue fractor at Palermo) 880 miles, Millosevich 630 miles. Secchi, comparing it with the first satellite 13 : 5.7 : 218.5 of Jupiter, estimated the diameter at 450 miles, and 7.0 8.5 12 : 54.2 thought the planet "di colore ranciata carico,' though it is usually considered pure white. Vogel considered that his spectroscope showed distinct traces of an atmosphere. At the time of opposition broader; but it is accurately placed south of the Mags. bright rings when they enter on the ball. The must figure, it be remembered, is inverted. Observing with a 6in. refractor, I have not been Sagittarii 40 110: 258 able to detect any difference yet in tint between the crape ring where it crosses the ball, and the shadow of the system of rings; but I can trace the bright rings, though very narrow, right across the ball. Besides the belt shown, I have, on one night in April, seen a second belt more to the south. Generally, the south hemispheroid of Saturn has seemed darker than the north; but it must be noted that this may be an effect of contrasting the southern part with the bright equatorial belt, and Sh 264 the northern part with the very dark shadow of the (8.0 mag. has a very minute comes at about 330-0° : 4) Vesta will be 45.7s. p., and 1' 38" N. of 15 Sagittarii, ring system. The principal division of the rings may be traced much further than is shown in the 48 drawing, and there is a decided difference of bright-3 246 ness still between the inner and outer bright rings, U Sagittarii. the latter being paler. Does M. Petitdidieu observe with a reflector or a refractor? Would he, in his next letter, state the aperture and focal length of Alex. Freeman. his telescope? Marston Rectory, Sittingbourne, May 5. PATH OF VESTA. [32295.]-THE accompanying maps (which I hope will be more clearly engraved than the one showing the path of Uranus in the ENGLISH MECHANIC for February 6th, 1891, Vol. LII. p. 505), are intended to show all stars down to 75 mag., and a few fainter ones, near the path of Vesta, from May 16th until July 16th, 1891. The plans of the stars are taken mainly from Schönfeld and Yesnall, and are plotted for the epoch 1855 0, to which epoch, of course, the path of Vesta has also been reduced; but the stars can easily be brought up with sufficient accuracy for identification to 1891.5 by applying a correction of +2m. 9.5s. in R.A., and +1'10" in decl. to the centre of map 1, and +2m. 12s. in R.A., and 13" in decl. to the centre of map 2. All known pairs within the limits of the maps (except those included in clusters) are shown, in which the primary does not fall below 75 magnitude, all known variables, and all nebula and The following data of the double and variable stars shown may be useful to the intending clusters. (A minute pair between, and other comites.) at 9h. 50m. p.m. on June 21st. She will be in Hardly any variation since 1870. Vesta will come into opposition on June 23rd, THE SUN. [32296.]-THE subject of my letter is on the nature, properties, and attributes of the sun, and here it will not be out of place to preface the following remarks by recording the manner in which the subjects first engaged my attention, and, I may further add, that about the time (1883), when the question was first brought under my notice, I unfortunately became the victim of impaired sight, from which time to the present I have been totally incapacitated from reading or consulting any author, so as to improve the little knowledge I In the summer of that year (June, 1883) I previously possessed on the subject. attended a lecture by the late lamented Mr. Proctor doctrine he then and there propounded was to the on the subject, which much interested me. The following effect-viz., that the sun is an incan descent body, and that the consumption of that body, incident to the combustion, was made up by the falling-in of other bodies to the gigantic mass of fire. I came away from his lecture disappointed and dissatisfied with the theory he enunciated. From that time to the present the subject has occupied more or less of my thoughts, reflections, and reasoning powers, such as they are, to find a way to acquiesce in his opinions; but the more consideration I give to the subject the more remote does any agreement seem capable of being arrived at. Mr. Proctor's theory I may take to be, from his high standing in the scientific world, the universally received opinion of the day. Let us then inquire into its merits, and the first question is, What is the radiation of heat? It is a question with me whether this radiation would extend within millions of miles to the planet we inhabit. What then, in such a case, would be the condition of the more distant planets? Inhospitable regions indeed they must be, and incompatible with the support of animal life of any kind or genus with which we are acquainted. It is also an undeniable fact that, the nearer we are to the source of heat, the hotter it is. What, then, is to be said of the planet Venus, which is millions of miles nearer to the source of that heat than we are, and yet she is said to be enveloped in snow, evidently showing that the climate is of a much lower temperature than ours. Next, as to the falling-in of other bodies to meet the demand, this theory is a violation of the law of Nature; that law is simple, certain, economic, and permanent-"in secula seculorum"-whereas the law that would govern the accepted theory is complex, adventitious, wasteful, and ultimately doomed to an inevitable finality. In fact, my opinion is that this finality must have been the result thousands of years ago, and chaos, in such a case, would reign supreme. Having thus, to my own satisfaction, at least, disposed of the prevailing theory, it devolves now upon me to find a more consistent one, and this I will now attempt to do, with much deference to the opinions of others. In the first place, the conclusion to which I have arrived is that the heat and light we derive from the sun is lenticular, in which case it is well known that the further removed we are from the source of that light, the warmer it becomes, provided we are within the scope of those rays, and by parity of reasoning, the nearer we are to the source of that light the colder it is: this at once would explain the cause of the relative temperature of Venus and our own planet, and, at the same time, forces upon us the conviction that the Georgium Sidus may have as warm and temperate a climate as our own. another fact that goes far to prove that the light and Here I may mention heat we derive from the sun is not derived from combustion of any kind; it is a well-known fact that the human eye cannot bear the rays of the sun for a second of time without inconvenience, and even of pain, whereas the light from combustion is perfectly innocuous to the human eye, and can be tolerated for any length of time. The next part of my subject is more speculative, and can only be solved by analogy, and no doubt the question will be asked how I account for the light and its mode of propagation. There is little or no doubt that the light is of an electric character, and that it is generated within the body of the sun, probably caused by the movement of its atoms and molecules, and this movement or attrition evolves the electricity. This is a mere suggestion, and I presume it must probably remain a mystery to the end of time. MAY 8, 1891. o'clock last night, was allured into scheming a workshop motor, and now, though pretty wide Your correspondent, unable to sleep till one awake, the prospect has not quite dissolved into the land of impossibility, and it may perhaps interest some of your readers to hear of it. its virtues is rather too troublesome to look after when the mind is bent on an intricate piece of work. It is not a steam-engine-that old friend with all Nor a gas-engine-that stinks, and is a nuisance in a small workroom. Nor a hot-air engine-that takes up too much room. Nor a water-motor-that most convenient and clean motor is unequalled where there is a natural fall of water, but with water at a shilling per 1,000 gallons, 'tis too expensive. Nor even an electro-motor-we have the electric light laid on, but it is an intermittent current, and only comes on at dusk, so it would leave one helpless during the day. the undulations of the surface of the sun, which grand discovery of the night, how the prospect cannot be supposed smooth like a billiard ball, fades away! but having its mountains and valleys, and each stance has been forgotten; the laws of nature, so one of these may form a lens of variable force. Next obligingly indulgent a few hours ago, are again as Some very simple law or circumpart of the subject-viz., the simultaneous summer required, and the patent agent will receive no we come to the consideration of a very interesting inflexible as ever; the drawing-board will not be and winter which each hemisphere enjoys, and there application, for the castle of cards has fallen. are several phenomena which must be referred to to account for this. First, the earth encounters at experience like this, and how often have we resolved each end of her orbit an impediment to her progress we will go to sleep the next time the mechanical Who of your readers has not passed through an by having to encounter a comparatively sharp curve will-o'-the-wisp seeks to lure us to the land of in her orbit; the effect of this curve is to change headache and disappointment? the axis (a friend-a F.A.S.-emphatically denied to me that the earth does change her axis). To settle this question, let us take the case of an acrobat riding a horse in a circus. Everybody is familiar with the position of the horse and its rider during this ride-viz., that the bias is decidedly towards the centre of the ring, and the cause of this is the centrifugal force, which traverses both horse and rider up to his head; and the centre of gravity, or, in other words, the axis is thus changed; it is therefore impossible, in my opinion, that a body like the earth, travelling at the rate she does, can possibly encounter the smaller segment of this circle without a change in her axis. Now it is obvious in this case that if the orbit were horizontal, then one hemisphere would have two summers in every year, and the other hemisphere would have no summer at all (and it may also be added that in the case of the acrobat it would be a continuous summer, as the axis never varies); but Nature has wisely provided a remedy for this, and this manifests not only her wisdom, but her justice, in the dispensation of her blessings to all her creatures alike, without fear or prejudice. This end is attained by the position, or rather obliquity, of the orbit. I do not know what the degree of this obliquity may be; but it is certain that it is all sufficient to meet the object for which it is intended. The incidence of the centrifugal force is at each end of the orbit, on the Equator of the earth, and in the one case its course is upwards, and that hemisphere is thrown forward (and the corresponding one backwards, course), and here the upper hemisphere receives the rays of the sun in a concentrated form, and has as a matter of her summer; at the other end of the orbit, the centrifugal force travels downwards, and that hemisphere is thrown forward, and thus she has her summer while the other hemisphere has her winter. Thus each hemisphere has its summer and pipes passed down the chimney and filled with its winter at one and the same time, and that at water; then have two water-motors, one at the top First, by means of water. each end of the orbit the intervening space is a Have two lin. iron comparatively straight course, and here the earth down one pipe and up the other, and the second the one hemisphere and a spring to the other. recovers her perpendicular, giving an autumn to one in the workshop, to receive the water under to be driven by the wind-engine and force the water by its critics, and more particularly by those deter-see; no bearings to oil, no gearing to vibrate and I have no doubt my paper will be severely handled deliver or exhaust into the other. No shafting, you pressure from one pipe, extract its power, and mined to adhere to their old faith, rightly or wrongly. I have not in any part of my paper, I week, perhaps, to the roof to oil the machinery, and believe, violated the law of nature; and hence I that is all; no charge from the water co., as the cause annoyance in the dwelling. fear no criticism, but can bear a slap in the face, same water goes round and round. A visit once a probably, with more equanimity than those in the know how water hates to be hurried; in a high meridian of life whose nervous susceptibilities are wind the machinery would not race, but the water more tender than those of a Moreover, we Nonagenarian. would check the motors and act as a break. + 52 53 + 55 ::::::: METEOR RADIANTS. Date. July 8, 11 Denning. Denning. Denning. Denning. July 31 Heis. .. Aug. 20, 29 Tupman. Corder. Sawyer (2nd cat.) stand the point at issue as to the shifting of radiants [32297.]-I THINK your readers will better underby giving the particulars of what appears to me to be a stationary radiant, but the various observations comprised in which would, no doubt, be If this be admitted, and also that the light is within Position. differently classed by Mr. Denning. the body of the sun, it stands that the sun must be 8° + 54° (or its outer covering at least) perfectly transparent, giving the whole sun the appearance of a 3+ 49 body of fire. This appearance is probably the cause of the delusion, and of the palpable mistake of its 5+52 being considered a body of fire. At Mr. Proctor's 7 lecture alluded to, he exhibited a map of the sun 8+ 52 Sft. or 10ft. in diameter, and this map was studded 3+49 all over with what I may be allowed to call, for the 3+ 49 want of a better term, nodules, of an irregular, circular form, each one of which, in the position in which they occupy, I should think must be as large 5 as our earth. Now, it would be an interesting 6 + 50 question to ascertain, as far as possible, what these 5+ 54 nodules really are. For this purpose, I would ven- 5+ 49 ture to suggest that the best defined one on the 5+ 50 map should be selected and photographed to the 7+ 51 diameter of one foot, and that a series of these, 5+53 graduated from one foot to six, should be taken, 5+52 and each one examined by a powerful microscope. Something might be eliminated from this process; but I do not vouch for any result. Let us here refer to what the spectroscope reveals with regard DREAMING OF A WORKSHOP MOTOR. to the materials of which the sun is composed. I do not remember all those that are recorded; but before the mind of the would-be inventor when he [32298.]-WHAT brilliant ideas display themselves prominent among them are those of silex and ought to be asleep; how the inexorable laws of sodium, chiefly the very ingredients of which trans-nature become kind and seem to range themselves parencies are manufactured. I would suggest the on his side; how he wishes for morning that he experiment of passing the rays of light emanating might get up and put his ideas on paper and secure from combustion and that from electricity, and to his patent! But, alas, when morning dawns, and what the product of each would be in the spec- the moment has come for action, the time for and which approaches nearer to the light we dreaming gone; the mind, missing its accustomed From the sun. These nodules may probably rest demands more sleep, and when at length the ered to be lenses; but setting this aside, sleepy eyes are open, and thought recurs to the Oct. 15, 20 W. H. S. Monck. engine-"Well, of all the "-Stop a minute, and let me tell you how I propose to arrange matters. No, it is only a mode of using a windmill or wind the roof. Our house is by the sea-side, and there are few days in the year when there is not a little The idea was suggested yesterday by a visit to wind. The workshop is in the basement, and the first difficulty was to arrange for conveying the power from the roof through three intervening stories. A vertical shaft is not to be thought of; we cannot cut the house up nor have any vibration of gearing, &c. the roof-could that be utilised? it would be very neat, for nothing would appear outside or inside the chimney flue from the workshop in the basement to There is, however, an unused house, but only the wind-engine on the roof. Can the power go down the chimney? I think it can in two ways. Second, by means of air. motor on the roof a compressing air-pump, and for Substitute for the just like a steam engine, to be driven by compressed also for the motor in the workshop, a little engine, the two lin. pipes in the chimney, one fin. pipe; air; or there might be one such little engine to each the workshop, which it would cool in summer; or, machine, the exhaust air simply discharging into if preferred, it might exhaust into the chimney. Here, too, you would have no heat, no smell, and only to turn on your tap, and off you go. But there is another advantage with the air which must be mentioned: and that is, that you can have a metal drum to contain a reserve supply-enough, perhaps, for an hour or two's work. This adds very little to the expense, and almost makes one independent of the uncertainty of the wind. The drum might be gradually filled during the night, or at any time in the 24 hours when there was enough wind. When full the wind-engine would be checked, and would only turn enough to supply the leakage. Whenever the lathes, &c., were wanted, there would be the power ready. at this satisfactory conclusion, and finding it was Having arrived now one o'clock in the morning, I took two pillules of aconite 2x, and was soon asleep. Now as to the cost of all this. I fear here is the "E.M.," and do not know what they cost, 1 [32299.]-I AM sure that all students of lunar surfacing must be very much obliged to Mr. Ranyard for his very lucid remarks in recent letters on lunar atmosphere and temperature. The questions which he has dealt with so clearly are of a very abstruse nature, and exceptionally difficult to convey to ordinary persons unused to mathematical formula, and, for one, I beg to thank him for making difficult problems so plain. If we can only manage to stick to the main S. E. Peal. THE CAUSE OF RECOIL. [32300.]-REFERRING to letter 32283, I quite saw, he (the photographer) would take photographs question, and avoid going off into side issues, we shoot sometimes with Gras rifle, and other times This seems to me to be the weak point in the may yet, I hope, manage to make some progress towards solving the great lunar enigma. Hitherto my work has been almost exclusively confined to the elucidation of how the several unearthly features which we see on our satellite could be explained by a theory of glaciation. I am not qualified to discuss deeply the question of lunar temperature, and when, in 1884, I found that Prof. Langley was at work on it, I confined myself to that branch of the subject which I felt more capable of dealing with. The solutions for the various peculiar features, which slowly came about, seemed to me to show such a remarkable tendency to support the general view, they fitted into their appropriate places so like portions of a great puzzle, and illustrated each other so beautifully, especially as a time series, that although I conld not give the mathematical solutions or data which Mr. Ranyard so clearly furnishes, yet I felt I was (in the main) on the right track, and that eventually, perhaps, some form of glaciation might solve the enigma. No doubt some portions of the subject must ever remain subject for speculation; but the accumulation of probabilities, as in other branches of science, will do much to supply the place of actual demonstration. One thing it seems most necessary to remember-i.e., that in speculating in regard to lunar phenomena, we must not apply too rigidly our terrestrial analogies. The smallness of the globe, and (practical) absence of an atmosphere are two features which alone would profoundly modify terrestrial phenomena. with the Lebel, whose bullet is two-fifths lighter "H." writes: "The gun itself forms the movable cannot agree with "H." when he says: "Nor Elève a l'Ecole des Hauts Etudes Industrielles, [32301]-LIKE your correspondent" H.," I fail Velo. THE MONGOOSE: HOW SHALL I [32305.]-IN last week's issue of the "E. M.," our friend "Eos" wrote an interesting article on them as ferrets, especially if they become tame, so the mongoose. I was struck with the idea of using I forthwith got one. It arrived after 21 hours, per parcels post, not what I expected-half-dead with cold and fear, but lively and vicious. I feel in the happy position of the man in the story who conjured up an evil spirit, which entirely satisfied his curiosity by scragging him. I have got the beast, but how to tame him I don't know. At present, he sits and growls like a dog, and spits like a cat. It is curious, very. Really I think that if he can be brought to a reasonable frame of mind, that he will prove both amusing and useful, for he seems quick and strong. so small a matter, but I thought that others might, I must apologise for occupying so much space on like myself, fancy such an animal, and would feel interested in my little experience. Mongoose. THE COST OF ELECTRIC LIGHTING. The lessened effect of gravitation we may in some things allow for correctly, in others not; but the almost complete absence of atmosphere is such a novel feature, that our terrestrial analogies must be accepted with caution. The great question of temperature evidently depends on the presence or absence of atmosphere: ours acts like the glass of a hothouse, permitting the sun's heat to enter, but preventing its return again by radiation. Take away the glass, or our atmosphere, and radiation is unfettered; the heat can pass off again as rapidly as it falls, or nearly so. It is received from one small portion of the heavens, the sun's disc, but can be radiated off again in all (available) directions. I have never, to my knowledge, assumed, as "Ja. Ha." says, that the radiation, or "heating power of the sun is excessively small." Again, our atmosphere does not act equally, as "Ja. Ha." seems to imply, on incident and radiated heat. It permits the solar rays to enter pretty freely, but after they have warmed the earth's surface, it distinctly retards the radiation of this heat back into space, and prevents the surface cooling rapidly, as it otherwise would. The evaporation of ice or snow under sunshine also depends on the temperatare; and the viscoscity or rigidity of ice equally so. This latter is not, I think, as yet generally known, and when it is, will probably tend to remove one great difficulty in accepting the view that the great littoral ranges on the moon are vast snow deposits. When we bear in mind the probably low tem-questions the visibility of spermatozoon under a especially the arc light, for home production, that [32302.] RECOIL is caused by the pressure exerted on the bottom of the bore of a gun by the combustion of its propelling charge, and occurs immediately on ignition. The pressure is equal in every direction where the charge is situated-laterally on the sides, horizontally on the bottom of the bore and on the base of the projectile. W. J. F. MICROSCOPICAL. [32307.]-IF Mr. Thos. Fletcher, or "Incans," who writes under the above heading on p. 205, will turn to p. 307, "Electric Light Installations and the Management of Accumulators," they will see that Sir D. Salomons shows that the gas burnt in a gas-engine and in turn produces electric light, more light is produced by the electric light than if I never saw the filamentary appendage men- burnt under favourable conditions in the gas tioned by Mr. Nelson; but if your correspondent burners; but this, of course, is not on the company will swing the mirror aside, so as to get dark-principle, and only the cost of production. ground illumination, and the preparation has a cover-glass upon it, he will have no difficulty in satisfying himself on this point. It is years ago since I first so saw it, and I was at the time surprised, as the form is clear under a lower power than the one mentioned. W. M. B. perature, this non-viscoscity of ice below zero, the Why is it that on the entire visible surface we do not see a single instance of a large circular sunk plain. 30 or 40 miles in diameter and 4,000ft. or 3,000ft. deep, without a raised ring? Why is there this persistent, and seemingly necessary, structural association, unless it is that the ring material has been derived from the inclosed excavation? Why do they fit each other, as a rule, so accurately? It is surely no slight on the many eminent men who in the past have lived and died working for a solution new theory of Indian jugglery has lately been J. Vinicombe. DISSIPATION OF ENERGY. [32308.]-ARE not the ideas on this subject mere speculation before knowledge? Energy is tending in all actions to dissipation, and to radiation into space. But all the bodies in space are also constantly receiving energy from space, and it would appear that space ultimately means, for each body, a closed sphere, which must absorb and return all energy which traverses space. We know little about the means nature may have of reversing the process called "degradation of energy"; but we do know of one process, viz., the growth of vegetation, and we may safely rest in the belief that the power which originated the universe can be trusted to keep it going. If that belief is not well founded, it is of little importance to us what is to become of the universe. It will last our time, unless the Rev. Mr. Baxter is correct in his remodelled calculations. The subject leads into the interminable question of force and energy: interminable because it is one of different meanings applied to words, and different words attached to conceptions by different people. In ordinary language, force, energy, power, and strength, and probably several more, are pretty nearly synonymous and interchangeable, as, in fact, they are all founded upon the one fact of work done. In science, for the sake of convenience and exactness, they are differentiated, so as to express causes and effects, time of operation, and so on; but that does not alter the fact and the underlying truth that the one meaning of them all is, ultimately, energy and work done. If we look at the real meaning of terms, we may see that force is chiefly a mathematical abstraction which expresses the mode in which energy acts, and its relation to matter. It expresses energy or its capacity as a degree, instead of as a quantity, and so enables it to be more conveniently used in calculations. But as is often the case with abstractions, the rigidly orthodox convert a symbol into a reality, and treat "force" as an existence. "W. J. R.," 32234, p. 160, seems to fall into this error, when he says, "upon what evidence is the idea based that force is dependent upon energy in any way whatever?" Well, the lifting a weight generates a force by the energy stored in the act of fifting; the force of gravitation can only give back that energy. The pressure of steam in a boiler is a force, but its existence is due wholly to the energy charged upon the water by the fire. In like manner every so-called force is related to and dependent upon energy supplied to it in some way or other. True, there are what we call the forces of matter that is to say its properties, of the causes of which we know nothing. But that is where the confusion of words and thoughts comes in. The forces of the mathematician are not these fundamental properties of matter, but merely a symbolic expression for the mode of action of energy operating through Sigma. these functions of matter. THE DISSIPATION OF ENERGY. [32309.]-I COPY the following from the sixth edition of Ganot's "Physics," p. 398, par. 462 :"Rankine has the following interesting observations on a remarkable consequence of the mutual convertibility which has been shown to exist between heat and other forms of energy. "Sir W. Thomson has pointed out the fact that there exists at least in the present state of the known world a predominating tendency to the conversion of all the other forms of physical energy into heat, and to the uniform diffusion of all heat throughout all matter. mon to the class, and all the relations of causation 66 Chemistry also introduced us to still another kind not so much have mattered, as all these might and ness. free, might be substituted, but they would hardly be an improvement. Potential energy was, Í believe, first proposed by Rankine, and as it has been adopted by Clerk-Maxwell (who, if my memory serves me correctly, somewhere terms it "a felicitous expression"), it is hard to see what we should gain by trying to get rid of it. It is, in fact, now in common use, so if we object to it we have not only to find another for the thing which, after all, wants some name, but also to face the inconvenience of changing the terminology. 61, Fairholt-road, Stamford-hill. W. J. B. myself made a rather unfortunate blunder. The P.S.-In my last letter, either the printer or word "requires," in the 28th line from the top on 205 has become "desires." p. has a rather objectionable implication as it stands, perhaps those who have read the letter will kindly As this latter word substitute the word indicated.-W. J. R. A FRICTION-GEARED LATHE. old and forgotten periodicals, may be of interest to [32311.]-THE following note, by a searcher in your lathe readers. It is a method of doing away with cone pulleys and belts on lathes. I quote the words of the writer, as found: I am always interested in novel ideas, even though they may not always be practical, and are sometimes a trifle antiquated. In looking over a volume of the Mechanics' Magazine for 1833, I head of "A Superior Turning Apparatus without a came across the following suggestion, under the Band," in which the writer, whose identity was not known, described his suggestion or plan in the following manner :-The illustration shows a plan W M B R The roller R is kept in contact more or less strict according to the kind of work done, and is also varied in its position with regard to the centre of the wheel in proportion to the velocity the work is to have in turning. "The form in which we generally find energy indeed all the forms of what we now call energy originally collected is that of a store of chemical were, in the absence of any term to properly "forces." By that time classify them, dubbed power consisting of uncombined elements. The combination of these elements produces energy "force" had come to denote so many things that its in the form known by the name of electrical currents, and despite all that has been done to bring order connotation seemed getting to the vanishing point, part only of which can be employed in analysing out of this chaos, the confusion is prevalent still in chemical compounds, and thus reconverted into a store of chemical power. The remainder is necespopular language, cropping up with a most vexatious sarily converted into heat. A part only of this heat regularity, too, in places where we might expect can be employed in analysing compounds or in better things. The turning point in straightening reproducing electric currents. If the remainder of out the matter was undoubtedly the introduction by for doing away with the use of the band (belt) in the heat be employed in expanding an elastic sub-Dr. Young of the term energy, since adopted by all turning, and for gaining beside advantages the band stance, it may be converted entirely into visible the writers on physics who have dealt with the never could have procured. W is the wheel taken fundamental concepts. This happy inspiration out of its old position and placed horizontally, inmotion, or into a store of visible mechanical power (by raising weights, for example), provided the enabled a better classification and a clearer under-mediately under the mandrel. D is the mandrel, elastic substance is enabled to expand until its standing to be arrived at, albeit with extreme slow- elongated so as to stretch entirely across the face of Under the new term has come to be classed the wheel, and R is a friction roller (or wheel) temperature falls to the point which corresponds to the absolute privation of heat; but, unless this all those modes of motion which are able to made adjustable to any part of the mandrel, so as condition is fulfilled, a certain proportion only of accomplish work. In fact energy is usually defined to compel it to revolve with it. The face of the A further ad wheel is turned perfectly plane, and the wheel the heat, depending on the range of temperature as "the capacity of doing work." through which the elastic body works, can be con- vantage of the use of this term is that force, instead itself should, along with the roller, be made of verted, the rest remaining in the state of heat. On of being made a sort of hack term of, is restored to such materials as unite to produce the quality of the other hand, all visible motion is, of necessity, more nearly its older meaning, and can be used to generating the greatest quantity of friction among ultimately converted into heat by the agency of signify those attractive influences, whether affecting themselves. friction. There is, then, in the present state of the masses, molecules, or atoms, which possess intensity known world, a tendency towards the conversion only, and cannot be expressed in quantitative terms. If these ideas be kept in mind, there need be no of all physical energy into the sole form of heat. "Heat, moreover, tends to diffuse itself uniformly confusion on the main subject; and one thing stands by conduction and radiation, until all matter shall out clearly at least, as we consider the order of have acquired the same temperature. There is, nature. It is this. So far from force and energy consequently, so far as we understand the present being "different states of the same thing," they are at eternal war with each other. Sometimes condition of the universe, a tendency towards a state in which all physical energy will be in the victory inclines to the one, and sometimes to the state of heat, and that heat so diffused that all other; occasionally as in other conflicts a drawn matter will be at the same temperature; so that battle may be said to result. This happens when there will be an end of all physical phenomena. force reduces energy from the kinetic to the potential state. This is effected by some form of energy altering the configuration of a material system in opposition to its forces. The energy is thus stored, and on the restoration of the original configuration reappears. It is this that gives rise to the appearance of force producing motion. In reality the motion is being reproduced, and it is always found when the case is examined carefully enough that this is what is happening. The term potential energy has been much [32310.]-IN a further interesting letter of objected to at various times, one of your corre"O. T. O. H. P." (32272, p. 201) he raises ques-spondents I see roundly declaring that he does not tions concerning definitions of force and energy believe in it. Well, if that be really his view, that seem to require a word or two of comment. perhaps he would kindly tell us in what way he Perfect definitions are, of course, to be expected in regards dynamically such things as a piece of coal, any department of science only when the know- a quantity of gunpowder or food, or, if he prefers ledge is perfect also, the definition summing up the a simpler case, a pile-driver with the weight on the results of the inquiry. As J. S. Mill well remarked hook at the top. If it be only the term, and not (Logic, Book IV. chapter 4): "In order to judge the thing, that is in dispute, other pairs of terms may finally how the name which denotes a class may best be used to signify the two states of energy. Dorbe defined, we must know all the properties com- mant and active, static and dynamic, bound and "Vast as this speculation may seem, it appears to be soundly based on experimental data, and to truly represent the present condition of the universe so far as we know it." Taking the word "universe" in its fullest astronomical sense, in my humble opinion the above leaves nothing more to be said. Bogleboski. But these are not the only advantages of this arrangement: there are others peculiar to it, and perhaps even more important. This position of the wheel offers facilities for giving various independent motions to the cutting-tool. To give one instance: Screws of every variety of thread may be cut by this arrangement. To do this, another frictionroller must be applied, whose axis of adjustment is in the direction of the radius to the wheel. Let there be also a wrest cut into a screw fixed before the work so as to revolve. Its head may be con nected with the axis of the roller by a Hooke's universal joint or by bevelled tooth-wheels, and so every adjustment of the roller will vary the velo city of the revolutions of the screw wrest, and with it that of the cutting-tool, which it may be made to carry along with it. be Many such independent friction-rollers may placed on different radii of the wheel, and so 3 multiplicity of various motions may be generated. each separate motion itself variable ad infinitam. The modern development of the lathe has, of course, been such as to entirely do away with such an arrangement as described by the above writer, and it is not because of its having any value in thre connection that it is mentioned at this time. There are, however, certain principles involved which have a value that may be realised by those of to-day who are working out new ideas, and as I was interested in it myself as a matter of history in connection with early mechanical developments, I have given it here, hoping that others may be equally interested, and possibly aided in one way or another. T. M. also for making up for the wear of the stop. The AN UNDERSHOT TURBINE. [32312.]-THE accompaning drawing shows an undershot turbine of 5H.P. for a fall of water 3ft. high. The turbine is placed in a bricked pit, F, level with the ground. The lower part of the turbine is a cylinder, A, in two parts, top and bottom, with an opening, G, by which the water flows into the turbine. On top of the cylinder A is placed the guide cone B. over which is the drivingwheel C, fastened to the vertical shaft H. The driving-wheel works in a loose case made of sheet The top end of the upright shaft H is carried by iron, D; one side of the case has got a trough for the triangular frame 0, 0, 0. One corner of the carrying the water from the turbine; this case is triangle is bolted to the top frame of the flume, bolted on to the top flange of the guide cone B. and the other two ends rest on the columns P, P, For carrying the vertical shaft H the centre of the which columns rest on lugs Q, Q, cast on to the guide cone has got a boss cast on it in which is cone B. In the section of the drawing the columns placed the step a; this step is prevented from turn-are punctured to show them, but they stand as ing round by a key, but can be raised or lowered by the short spindle C, the lower end of which works in a step in the small cylinder E, placed in the lower body of the turbine A. The cylinder E is divided into two parts by the partition e, the top is closed by the guide cone B. In the upper space of the cylinder E is placed a couple of mitre wheels, one of which is keyed to the spindle C, the other on to the shaft d. The top end of the spindle C has got a coarse thread cut on it, which screws into the bottom end of the step a, by turning the shaft d, and through the mitre wheels the spindle C the step is raised or lowered, by which you can regulate the space between the driving-wheel and the guide Cone, as the space between them must be very small, shown on the plan of the turbine. R is the A STATIONARY WATER-MOTORRECOIL: CAUSE AND EFFECT. [32313.]-THERE are several reasons why the motor described by Mr. Wraight (in 32278) would not work. One reason is that the motor would be a solution of perpetual motion. It must be remembered, moreover, that the pressure in a liquid acts only normally to the surface of an immersed or partially immersed body. In the case of the circular wheel, the normals all point to the centre or axle, against which point all the pressure is exerted, and being resisted is of no avail. is caused simply by the explosion of the powder. I agree with "H." (32283, p. 206) that the recoil This being granted, the recoil would begin directly the powder exploded. If the gun be fired without a bullet, there is next to no recoil, because there is no resistance. But if the recoil were caused by the inrush of air after the explosion, the recoil would be apparent with or without the bullet. Again, let the gun be loaded up to the muzzle with bullets and fired: assuming that the gun did not burst, the recoil would be tremendous, evidently showing that it is dependent upon the mass of the projectile. This is also the opinion of Balfour Stewart. Caldemone. [32314.]-IN the machine under consideration no water is supposed to be used up in working it, nor is any kind of energy to be put into it, and yet the poor motor is expected to do work. "V. A. W.," letter 32278, says that the portion of the thin circular tube in the water will have an upward tendency, whilst the other side of the wheel will be attracted downwards by gravity. It is true that the water will exert an upward tendency; but this upward tendency is exerted upon the wheel as |