478 



TRANSACTIONS OF THE AMERICAN INSTITUTE. 



in, this perforation is covered with a diaphram when not in use. 

 Above this he places the conical mirror, the light from the mirror 

 below being sent up to the conical mirror and from thence to the 

 object Ijelow. Pie believes cloudiness will thus be obviated. 



Dr. Barnard thought the suggestion valuable, and stated he was 

 still experimenting in that direction. 



Dearborn Observatory at Chicago. 



Prof. T. H. Safford, director of the Chicago Observatory, gave 

 an interesting account of that new institution and the great instru- 

 ment of which it boasts. The Observatory originated in a move- 

 ment started some years ago by Prof. Forey, Avho gave a series of 

 lectures on astronomy in Chicago, and proposed to the citizens 

 the purchase of a telescope of Mr. Henry Fitz. A committee was 

 appointed to raise subscriptions for the purpose, and Hon. J. Y. 

 Scammon offered the means for the erection of the neces^sary 

 buildings. A committee was also appointed to investigate the 

 si^bject of telescopes, and the committee determined not to pur- 

 chase the instrument of Mr. Fitz, but to obtain, if possible, that 

 being constructed by Mr. Clarke, of Cambridge, Mass., which had 

 been ordered by President Barnard for the University of Missis- 

 sippi, but which was lost to its original purchasers by the occur- 

 rence of the war. The object-glass for this instrument is the 

 largest in existence — 18 1 inches in diameter. It was procured 

 with some difficulty, and the building to receive it was commenced, 

 and was completed last March, It is built of the limestone com- 

 mon in Chicago, and is situated at the southern extremity of the 

 city. The diameter of the tower is thirty feet, its height ninety- 

 six feet, which is favorable to observations, owing to the greater 

 stillness of the atmosphere. The object-glass of the telescoj)e is 

 of first-class excellence, so that full advantage is got of the aper- 

 ture. The focal distance of the glass is twenty-three feet. 



The subject of observation, with which the Professor has chiefly 

 occupied himself since the telescope was mounted, has been that 

 of the nebula?. He briefly gave an interesting account of these 

 observations, suggesting the question whether the immense num- 

 ber of the nebulae found near the pole of the milky way is not 

 connected with the number of the stars in the milky way. He 

 has found thirty-seven new nebula? not catalogued by Herschell, 

 and notices that many of those described by Herschell as very 

 faint appear but slightly faint, showing that the Chicago instru- 

 ment has greater optical power. 



