424 TRANSACTIONS OF THE 



perature of the air during observations, to prevent condensation of moisture 

 on their surfaces ? 



Mr, Fitz, — It has been thought of. 



Mr. Stetson. — You speak of the absorption of light by the reflectors, 

 do they not also absorb heat ? 



Mr. Fitz. — None ; polished surfaces do not. Parker's lens melted gold 

 in a decanter of water. The lower strata of air abound in impurities, and 

 injure observations. 



Prof. Hedrick described Steinhiel's silvering of glass speculums, as on 

 the side opposite to the light, as in common mirrors ; so that a fine polish 

 is presented. 



Mr. Fitz. — Outside the glass. 



Mr. Tillman. — Glass has one advantage over the metals, for telescopic 

 purposes, being less expansible, and strong enough to be made greatly 

 lighter than the brittle alloy used for reflectors ; and consequently it would 

 be much less liable to condense moisture on its surface, and would not be 

 injured, as they are, by wiping it off". 



Mr. Fitz. — The alloy reflectors are very sensitive ; the touch of the fin- 

 ger aff'ects them — slight variation of temperature cracks them. 



Mr. John Johnson. — What is the largest reflector now ? 



Mr. Fitz. — There is one in Paris of 19 or 20 inches ; it may prove the 

 best observer. To get rid of chromatic glasses, monochromatic have been 

 tried — yellow and red, for instance. We see better through misty air 

 with the red glass than the white one ; yet color is unfriendly to our most 

 interesting views, that is, the most remote, for we have fallen in love with 

 nebulae. 



Mr. Butler. — What is the actual power of the large lens ? 



Mr. Fitz. — It is according to its area. Rutherford's has a power of 900 

 times ; it magnifies a moon of Jupiter as large as our moon, and the spots 

 upon it. 



Mr. Tillman. — The question for next meeting — " Coal Oil." 



At 10^ o'clock P. M., the Club adjourned. 



H. MEIGS, Secretary. 



February 9, 1859. 

 Present — Messrs. President Pell, Leonard, Bruce, Witt, Seeley, Veeder, 

 Haskell, John Johnson, Shephard, of Chicago, Sykes, Stetson, Palmer, 

 Breisach, Prof. Mason, of Poughkeepsie, Mr. Dwight, of New Haven, 

 Prof. Hedrick, Tillman, Beid, and others — 40 in all. 

 . President Pell in the chair. Henry Meigs, Secretary. 

 The Secretary read the following papers, selected by him, viz : 



COAL OIL. 

 A gentleman in Baltimore is said to have invented a new retort for the 

 production of the oil, by which the light and heavy oils are separated from 



