296 POPULAR SCIENCE MONTHLY. 



as illustrated by the photographs themselves (compare Fig. 3 with 

 Fig. 4). The small cluster, which in reality contains several thou- 

 sands of stars, is resolved by Mr. Eitchey's photograph taken with the 

 large telescope into all its constituent parts, stars less than one second 

 of- arc apart being clearly separated on this great scale. 



Fig. 3. 

 Star Cluster Messier 11 and the surrounding milky way. 



Small scale photograph taken with portrait lens (Barnard). (The cluster, here about one- 

 sixteenth of an inch in diameter, lies just above the middle of the picture.) 



Having seen this illustration of the superior power of the large 

 telescope you may perhaps be interested to become more closely ac- 

 quainted with the instrument itself (Fig. 5). The great weight of 

 the 40-inch lens, amounting with its cell to half a ton, requires that the 

 tube which supports it, here taking the place of the camera box of the 

 previous instrument, shall be of immense rigidity and strength. This 



