574 



NA TURE 



[October ii, 1900 



will be compelled to offer them advantages at any rate 

 not inferior to those that they can find much nearer 

 home. 



The students of the Middlesex Hospital were addressed 

 by Prof. Clifford AUbutt upon abstractions and facts in 

 medicine. His concluding remarks with regard to the 

 value of research laboratories are significant, the lecturer 

 confessing that mere observation of disease and morbid 

 anatomy have taken us almost as far as these means 

 can do. Morbid processes should be tracked in their 

 earliest dynamic initiation in order that they can be 

 arrested in these stages. The clinical laboratory of a 

 county hospital should be the centre of enlightenment to 

 all the private practitioners of the district. 



The space at our command has only permitted us to 

 reproduce a relatively small fraction of the many interest- 

 ing and instructive addresses that were delivered during 

 the course of last week. It is sincerely to be hoped 

 that teachers and students alike have profited by them, 

 and that their united efforts will result in the addition to 

 the profession of a body of workers who will be in the 

 truest sense medical imperialists, and who, while work- 

 ing to the fullest advantage the store of learning they 

 have inherited, will not rest content with it, but extend 

 in all directions the empire of medical knowledge, even 

 up to the threshold of the temple of truth. 



F. W. TUNNICLIFFE. 



A NIGHT WITH THE GREAT PARIS 

 TELESCOPE. 



SINCE the final decision was made some years ago to 

 commemorate the Paris Exhibition of 1900 by the 

 installation of a giant telescope which should surpass in 

 size and power any other then in existence, so many 

 varied and contradictory statements have been quoted in 

 the Press, and even in many scientific journals, that a 

 considerable amount of scepticism has been inherent in 

 the minds of most persons interested in the matter. Much 

 of the inaccuracy is traceable to a rather loose estimate 

 being given of the magnification which it was hoped to 

 employ, it bei ng stated that the moon would be appar- 

 ently brought so close that any object of i square metre 

 area could be distinguished. By the extreme kindness and 

 courtesy of M. Francois Deloncle, to whose initiative the 

 entire instrument is due, the writer was enabled, not only 

 to thoroughly examine all parts of it during the day, but 

 also to take part in the practical astronomical use to 

 which it is already being put during every clear night. A 

 general view of the siderostat is shown in Fig. i, and the 

 inclusion of the attendant's figure m the upper balcony 

 will give some idea of its relative size. The masonry 

 foundation is about 5 feet 6 inches high, the extreme 

 height of the curved casting carrying the mechanism at 

 the back being about 34 feet. The circular glass mirror 

 seen between the upright fork in front is 6"5 feet (2 

 metres) in diameter, and about i r8 inches (30 centimetres) 

 thick, being silvered on the upper exposed side. When 

 not in use a large glass plate is lowered over the 

 silvered surface by a windlass worked from the gallery. 

 As the glass mirror weighs some 3600 kilogrammes, and 

 the iron cell and forked support about 3100 kilogrammes, 

 the friction on the pivot allowing rotation would have 

 been too great for accurate driving if some provision had 

 not been made for eliminating it. This has been success- 

 fully done by immersing the base of the fork casting in 

 a bath of mercury, contained in the circular part of the 

 front half of the main base plate, thereby relieving the 

 pivots of about 9/ioths of the total weight. The rotation 

 of the mirror in a vertical plane is also facilitated by the 

 counterpoise weights shown at the ends of the, levers 

 acting on each extremity of the horizontal axis passing 

 through the centre of the mirror. 



At the western side of the siderostat, above the 



handles moving the instrument in right ascension and 

 declination, are two telescopes, which by a system of 

 lenses and mirrors enable the observer to read the 

 divisions on two graduated circles without leaving his 

 position. By his side there is also a standard sidereal 

 clock and a telephone. 



Fig. 1.— The great siJ 



Leaving now the siderostat, and mounting the staircase ;i 



seen behind it, access is gained to the upper balcony ^ 



which runs round both sides of the whole length of the | 



building. Fig. 2 is a view taken from the eye-end of the : 



telescope, 200 feet away to the south, and the siderostat ' 



NO. 161 5. VOL. 62] 



id of the refractor, Paris, igoo. 



can just be seen under the arch at the north end. Above, '* 

 on the gallery, the circular object-glass is clearly shown |i 

 in its case. Two of these lenses are to be provided, one *j 

 specially corrected for visual work, the other for photo- \ 

 graphic purposes. The lens completed and in position? 

 is the latter. The carriages for holding these lenses in ^ 



