190 



SCIENCE 



[Vol. VI., No. 135. 



decided upon until both disks have been 

 carefully tested. The difficulties which the 

 glass-maker has to encounter in obtaining so 

 large a disk of crown-glass have been found to 

 be much greater than with the flint, and fif- 

 teen or twenty moulds are said to have been 

 ruined in the attempt to get them into the re- 

 quired disk-form. It is hoped that the glass- 

 maker will succeed in accomplishing his task 

 during the present season ; and, in that event, 

 the great telescope can readil}^ be completed 

 in 1887. Mr. Lick's trustees will then trans- 

 fer the establishment to the University of Cali- 

 fornia, and the observatory will subsequently 



ing-year may be found when the maximum 

 magnifying-power — about thirty-five hundred 

 diameters — may be advantageously employed 

 on the great telescope. The theoretical dis- 

 tance of the moon would then become about 

 sixt}^ miles, but the corresponding ideal condi- 

 tions of perfect vision can never be attained. 

 Making due allowance for the unavoidable 

 effects of the earth's atmosphere and other 

 unfavorable conditions, the observer might 

 expect to see the moon much the same as he 

 would without the telescope if it were only a 

 hundred miles awa}^ If, at the same time, 

 the moon happened to be at its least distance 



Fig. 4. — The Lick observatory. Interior of the meridian-circle house. 



be conducted under the control of the regents 

 of that institution. 



An inquiry often made, and a ver}' natural 

 and proper one, relates to the prospective ca- 

 pabilities of this enormous instrument, when 

 mounted in so favorable an atmosphere, and 

 directed to the moon. Every astronomer who 

 has observed the heavenly bodies from Mount 

 Hamilton knows that the extraordinary steadi- 

 ness of the atmosphere enables him to regularly 

 emplo3^ eye-pieces on his telescope which mag- 

 nify two or three times as much as those he 

 habituall}' uses for the same kinds of work at 

 home. It is thus not unreasonable to expect 

 thnt n few niohts in the course of each observ- 



from the e3'e of the observer, — about 220,000 

 miles, — and if the object on the moon were 

 suitabl}^ illumined by the sun's light, it is pos- 

 sible that details of its nature might be satis- 

 factorily made out, even although they were 

 no larger than some of the larger edifices on 

 the earth. 



THE GROWTH OF THE FRENCH ACAD- 

 EMY. 1635-1885. 



It is interesting to trace the influences by 

 which the French institute, V Institut de France, 

 as we know it in these days, has been devel- 

 oped from the French academy-, V Academie 



