instruments; ^l Draconis, from the equality of the disks 

 and softness of Hght, presented the finest appearance. 



y Virgines, with a power of three hundred and fifty 

 in either telescope, gave no certain indications of 

 being double. Some of the members of the com- 

 mittee were of opinion that it was slightly elongated. 



It was stated by the artist that his reflector would 

 divide stars distant 3" from each other. 



Estimating the distance of the stars observed by the 

 late observations of South, Struve, and Herschel, jr., 

 the committee were of opinion that his instrument is 

 adequate to the distinct division of double stars dis- 

 tant from each other 2". 5. 



The motion of this instrument, plainly mounted, was 

 steady, and with the finder, even without rack work, 

 objects were easily made to range with the centre, 

 or line of collimation of the instrument. 



The position of the observers with the Herschelian 

 telescope, was natural and easy in contemplating 

 objects having seventy or eighty degrees of altitude, 

 though quite constrained and inconvenient in using 

 the achromatic. 



The reflector gave a distinct view of land objects, 

 even when within one-fourth of a mile. 



Some light was lost by the position of the head, an 

 inconvenience partially obviated by making the end 

 nearest the object three inches greater in aperture. 



The Gregorian, which probably was not a very fine 

 instrument of its kind, bore no comparison in dis- 

 tinctness, or in quantity of light, with the Herschelian 

 telescope. 



From these trials, the committee are of opinion that 

 Mr. Holcomb has been entirely successful in the diffi- 

 cult art of polishing specula with the true curve, 

 which gives to the objects viewed all the distinctness 

 of figure that is given them by the best refractors by 

 Dolland. 



In one respect, the largeness of the field of view, the 

 reflectors by Mr. Holcomb have a decided advantage 

 over achromatics and reflectors of different con- 

 struction. The apparent diameter of the field of 

 view in the Herschelian being nearly double that of 

 either, with equal freedom from aberration. The 

 quantity of light furnished by the refractor was greater 

 with the same aperture, an important advantage in 

 searching for, and observing very minute objects. 

 This deficiency of light in the Herschelian for viewing 

 faint objects near the moon, or satellites near their 

 primaries, the committee are of opinion may be re- 

 moved by enlarging the aperture of the Herschelian 

 reflector to five or five and a half inches. 



The simplicity of the method of preparing and 

 mounting Mr. Holcomb's telescopes is worthly of 

 notice, since on this plan, the artist is enabled to 

 furnish for an expense of one hundred dollars, with 

 plain mounting, or of one hundred and fifty to two 

 hundred dollars, with more expensive mounting, 

 telescopes whose performance equals that of Gre- 

 gorians and achromatics hitherto imported into the 

 country at an expense of five hundred dollars. 

 By order of the committee. 



May 8th, 1834. William Hamilton, Actuary. 



[From Journal of the Franklin Institute, July 1835, new ser. vol. 

 16 (whole no. 20), pp. 11-13] 



Report on Holcomb' s Ke fleeting Telescopes. 



The Committee on Science and the Arts, constituted by 

 the Franklin Institute of the State of Pennsylvania for the 

 promotion of the Mechanic Arts, to whom was referred for 

 examination, two reflecting telescopes, made by Mr. Amasa 

 Holcomb, of Southwick, Hampden county, Massachusetts, 

 REPORT:— 



That the following description of these telescopes 

 is given by Mr. Holcomb: 



The two reflecting telescopes now submitted by the sub- 

 scriber, are constructed on the plan of Sir William Herschel, 

 having the front view. The largest has a focal length of 

 9)2 feet; the diameter of the speculum is 8)2 inches, and has 

 five astronomical eye-pieces, and one terrestrial eye-piece, 

 for showing objects erect; the lowest power is 57, the highest 

 900. The smallest has a focal length of 7 feet 9 inches; the 

 diameter of the speculum is 6^ inches, and has one terres- 

 trial, and four astronomical, eye-pieces; the lowest power is 

 60, the highest is 600. They are of the same kind as those 

 that were submitted a year ago, except the manner of 

 mounting, which is very different. 



Amasa Holcomb. 



On the evening of the 4th of May, the committee 

 met, by appointment, in an open lot south of the 

 Pennsylvania Hospital, for the purpose of testing the 

 performance of the telescopes, which had previously 

 been tried by some of the members of the committee, 

 and by other gentlemen, on the evening of the 2d. 

 The result of the examination was highly creditable 

 to Mr. Holcomb, and cannot fail to gratify all who 

 have at heart the advancement of astronomical science 

 in this country. 



The instruments, with powers varying from .50 to 

 600 in the smaller, and to 900 in the larger, gave satis- 

 factory views of the moon with a sufficiency of light. 



182 



BULLETIN 228: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



