80 [Assembly 



It is furnished with Huygen's eye pieces magnifyiug from CO to 

 2,000 time?, and anannular micrometer for measuring comets and 

 faint objects which do not admit of illumination. It lias a filar 

 micrometer furnished with a set of Ramsden's, or position eye 

 pieces, magnifying from 100 to 2,000 times, and also a clock for 

 moving the instrument corresponding with solar, lunar, and 

 sidereal time, by which the object is kept accurately within the 

 field of view. The hour, or right ascension circle, measures elev- 

 en inches in diameter, divided by half degrees and reading to 

 minutes. The declination circle is thirteen inches in diameter, 

 divided to half degrees and reading to minutes. There is also a 

 comet seeker of three inches aperture attached to the tube as a 

 finder. All the glasses are made from Guinand's disks. 



This instrument is the largest which has been made in the 

 United States, and in all respects accurately and most beautifully 

 finished. The base is made of ash in the form of the Munich in- 

 strument, and veneered with rose wood. It was made, we under- 

 stand, for Wm. Van Derzee, Esq., of Buffalo, for private use, at a 

 cost of $2,200. 



In our volume for 1819, w^e noticed an object glass C| inches 

 aperture, made by Mr. Fitz for the United States government, to 

 be used by the astronomical expedition. We are now permitted 

 to make the following extract from a letter written to IMr. Fitz by 

 James M. Gilliss, Esq., in charge of said expedition, dated at 

 Santiago de Chile, February lt5t, 1851. 



" There is no doubt whatever, that the object glass made by 

 you has sliown me more minutely and satisfectorily difficult 

 stars than that at Washington ever did ; yet it is prpper to say 

 at the same time, no systematic trial has ever been made by me 

 of the capacity of either glass. With your lens six of the satel- 

 lites of Saturn have been seen and the sixth star in the trapezium 

 of Orion without difficulty. There are occasions when the instru- 

 ment would readily bear a power of 800 or 1,000, and its con- 

 stant use would be amply repaid ; but the numerical force of the 

 expedition in assistants does not permit its employment except 

 for the series on Mars and Venus, and occasional occultations." 



A. C. 



