' 106' [Assembly 



So far, T have been unable to detect any evidence of veins or 

 other inequalities in the substance of the glass, which I look upon 

 as of rare purity. 



Owing to the great aperture of the objective, the disks of stars 

 are extremely small, thereby enhancing its power of separation. 

 I find in my notes of the measurement of No. 52 Orionis, whose 

 distance is 1"43. that with a power of only 100, they were 

 clearly separated, forming a beautiful miniature of Castor. 



The disks, in a good atmosphere, are round and small, with 

 power of 600 and 850. With the latter power I have dis- 

 tinctly seen the separation of the companion of y Andromedse 

 and w Leonis, neither of which have a distance at this time 

 greater than 0'"5. The elongation of these most difficult objects 

 is seen plainly with 400 -, with 600 they become notched with a 

 line occasionally seen between; with 850 they become decidedly 

 detached, whilst the disks are not larger than with 200 in my 

 old six inch telescope. I must add that neither of these stars 

 has been observed in what would be called a fine night. After 

 an account of the performance of this objective upon the two last 

 mentioned tests, it would be needless to accumulate descriptions 

 of its action upon z Cancri, e Arietis, 32 Orionis, the 5th and 6th 

 stars in tlie trapezium, &c., &c., which are in comparison easy 

 stars, and have all been shown with a power of less than 200. 



YoLi will be good enough to excuse the poverty of my list of 

 tests, which has been circumscribed by the unfavorable state of 

 the atmosphere during the short time since you delivered the 

 glass to me. Still enough has been seen to warrant my most sin- 

 cere congratulations upon the achievement of corrections in a 

 glass whose proportions presented unusual difficulties, hitherto 

 surmounted but in one other instance, a telescope made by the 

 venerable and learned Amici, of Florence, having exactly the 

 same ratio of aperture and focal length, viz, nine inches to nine feet. 



I hope at a future day to be enabled to present you with a more 

 extended list of tests of illumination. 



Yours very truly, 



LEWIS M. RURTREYIND. 



175 Second avenue. 



