SCIENTIFIC NEWS. 



[July 6, IS 



Kensington). All of these are fused on their surfaces 

 but the work of the friction being completed in so shortj 

 a time, the heat could not travel to the interior. I 



If so good a conductor as meteoric iron fails to carry/ 

 the superficial heat to its interior, how much less able is 

 so bad a conductor as ice to do the like. This may be 

 easily illustrated by placing a lump of ice in the midst 

 of a fire and watching the result. However fierce the 

 fire may be, the time required for melting the ice is con- 

 siderable, and proportionate to its size. 



We must also remember that ice has the advantage of 

 iron, not only in respect to specific heat, but also in that 

 of its great latent heat of fusion and evaporation. Putting 

 these together, those of my readers sufficiently interested 

 in the subject may make the calculation for themselves, 

 and will find that to melt and vaporize I lb. of ice de- 

 mands about three times as much heat as to fuse i lb. of 

 cast iron. Here, of course, I refer to the quantity of heat, 

 or heat-work, not to mere intensity or temperature. 



Besides this, Sir W. Thomson was wrong in assuming 

 that all the work performed in retarding the motion of 

 a meteorite, whether of ice or metal or any other sub- 

 stance, is directly converted into heat. It is evident that 

 some of the motion of the solid body will be communi- 

 cated to the air as mechanical motion ; how much I will 

 not attempt to calculate, but as the distance travelled in 

 the mobile air is great, the amount of atmospheric 

 commotion must be considerable. What may finally 

 become of that motion does not affect the question under 

 discussion, the hailstone being removed from the sphere 

 of such action before it is completed. 



I am aware that eminent men of science, whose views 

 I am bound to respect, interpret the doctrine of the con- 

 servation of energy in such a manner as to assume that 

 in every case where the mechanical motion of a body is 

 arrested, the whole mass of the body is necessarily 

 heated accordingly. I have discussed this question with 

 scientific friends in literal table talk, and find that such 

 discussion is instructive; it deals with one of the 

 grandest, I may say the grandest, generalisation of 

 modern science, the one which constitutes the philoso- 

 phical basis of all our science, and which should be clearly 

 understood by all. 



I will therefore make it the topic of more table talk in 

 this magazine. 



THE THIRTY-SIX INCH TELESCOPE 

 OF THE LICK OBSERVATORY. 



MR. JAMES E. KEELER, one of the astronomers 

 at the Lick Observatory, has recently communi- 

 cated to the Scientific American an account of the great 

 Lick telescope, from which we borrow the following par- 

 ticulars. 



The pier of the telescope is a rectangular cast-iron 

 column weighing 20 tons, built up of four sections rigidly 

 bolted together. The thickness of the iron is about i| 

 inches. The lower section, which at the floor-level 

 ' s 9 by 5 feet, expands into a broad base, 16 feet long 

 and 10 feet wide, resting on the solid masonry founda- 

 tion which forms the tomb of James Lick. This casting 

 weighs 5 tons, and is the heaviest single piece hauled 

 to the summit in the construction of the observatory. On 

 top of the pier is a balcony, surrounding the massive 

 head-piece which forms the support for the polar axis. 

 The upper section of the pier, 4 by 8 feet at the top, con- 

 tains the driving clock. A light iron spiral staircase, 



running from the base of the pier on the south to t>° 

 balcony, gives access to the clock-room and n y 



above, and adds greatly to the appearance of th c- 



ing. 



The weight of the pier is distributed over a number 

 of heavy steel screws in the base, which afford means 

 for the exact adjustment of the polar axis, but it is 

 possible that, after this adjustment is perfected, the base 

 will be set in cement, and the pier permanently fixed in 

 position. 



The telescope is intended to be moved by an assist- 

 ant stationed on the balcony which surrounds the top of 

 the pier. 



The makers, Messrs. Warner and Swasey, designed 

 the entire mounting, with the exception of the eye end, 

 which was made essentially from plans prepared by Pro- 

 fessors Langley and Holden. The telescope can also be 

 moved quickly in the ordinary way by the observer at 

 the eye end, although, as the whole train of gearing ex- 

 tending to the balcony must then be set in motion, this 

 cannot be done as easily as if the quick motions had not 

 been provided. A pressure of 10 lb. on the spokes of 

 the quick motion wheel on the balcony will move the 

 telescope in right ascension ; a pressure of 20 lbs. is re- 

 quired for the motion in declination. The telescope can 

 be reversed, or the same star brought into the field on 

 opposite sides of the pier, in a little over two minutes. 



The polar axis is a finely-finished shaft of steel, 

 12 inches in diameter and 10 feet long, weighing 

 2,800 lbs. It is pierced centrally by a 6-inch hole, 

 through which passes a shaft for communicating _the 

 motions in declination to the telescope from the balcony. 

 The polar axis turns in bearings of Babbitt metal, but 

 the greater part of the weight on its upper end (some 

 14 tons) is supported by a collar containing hard steel 

 rollers encircling the axis just outside of the upper bear- 

 ing, and carried by a lever which leads down into the 

 hollow head piece, and can be adjusted for tension. The 

 lower end of the axis is turned to a flat surface, and the 

 thrust of about 8 tons is taken by two rows of hard steel 

 balls rolling in concentric grooves. To the upper end of 

 the axis is bolted the cast iron cylindrical case, 9 feet in 

 length, which contains the bearings of the declination axis. 

 The declination axis is 10 feet long and 10 inches 

 in diameter, and is also made of steel. To one end is 

 bolted the cast-iron central section of the telescope tube. 

 The other end is just outside of the 6-ioot declination 

 coarse circle, and carries indices which point out the 

 approximate declinations. The coarse circle is fixed to 

 the declination axis case, and supports the rods which 

 carry the weights for counterpoising the tube. This 

 rod is made of a brass tube shrunk on to a steel core, 

 and the weights, which are in the form of circular discs, 

 travel on a thread cut in the brass. Each disc is 2 feet 

 in diameter, and weighs 240 lb. Eight of these discs 

 are required to counterpoise the telescope. 



The bearing of the declination axis toward the telescope 

 is relieved of the weight of the tube and its attachments 

 (about 4! tons) by a double counterpoise lever, one end 

 of which carries a collar with steel rollers, like that on 

 the polar axis, the other an annular iron casting weighing 

 500 lb., which surrounds the sleeve of the declination 

 axis just inside the coarse circle. The steel rollers 

 embrace the axis close to the telescope tube, and as the 

 counterpoise levers are always parallel to the axis, they 

 relieve the same proportion of the pressure on the inner 

 bearing in every position of the telescope. 



