Miscellaneous Intelligei 



V. MISCELLANEOUS SCIEXTIFIC IXTELLIGENCE. 

 1. Editorial Correspondence — The Spectroscope. — The following letters 

 from Professors Cooke and Rood contain interesting observations with 

 the spectroscope, which is hereafter to be regarded as an indispensable 

 auxiliary in the working laboratory. The instrument of Mr. Clark, with 

 ^'hieh Prof. Cooke's observations were made, has a prism of flint glass of 

 about four inches on each face which is built up of several thicknesses of 

 plate glass cemented together by Canada balsam. Tb.is construction 



tion are of no optical importance. 



Cambridge, July 28, 1862. 

 % dtar SilUman-.—l have a few moments, before leaving Cambridge for 

 the vacation, to make good my promise and give you the results of my experi- 

 ments with Clark's spectroscope. It has worked wonders in splitting up the 

 mious colored bands of the different spectra. You know that the yellow 

 sodium band is doubled. I have succeeded in separating them, at least a six- 

 teenth of an inch still retaining good definition. The red line of potassium 

 i|s also double, the two members being even wider apart than those of sodium. 



be deceived by the effect of diffraction similar to that described by Dr. White 

 >n a late number of your Journal. The most rem ' " -•-.•. • 



Dread orange band of strontium. It divides up i 

 lin„. -!":'' "^'^^^'ierfect^y simih 



B caught glimj.,., 

 that the results have not been equally satisfactory. In order to see them 

 ecessarv to reduce the width of the slit to about the same size as that re- 

 Ito show the Fraunhofer lines, but with the ordinary appliances long be- 

 ns point is reached the liffht from most of the bands has become too feeble 



r theory of Kirch- 

 "ofl- and Bunsen is evident Very truly, your friend, 



^ On prisms of Bisidphid of Carbon for optical purposes, (from a letter of 

 Prof. O. N. Rood to Prof. B. Sillima.n, Jr.). 

 P^ftr Professor:— I send you a stereograph of a large spectroscope with/oMr 

 fr^, which I have lately constructed for use in my optical studies VVh.ie 

 Jjy^eneral arrangement is similar in principle to that ^^P^^^^f^^^Jj^J-'^^ be 



of ca'rbr^ ^"^ ^""" '^■^''''^ °^ ^^^ P"^""^ '"'^ ''°"'^'' • ^""^ ^-'^^-'■-'-'" 

 ^^ j/nJ f ^/ The frames of 



^isulphid of carbon was poured in through 



glass, the angles being respectively, M , (.0 , 

 ,. L prisms were made of cast iron ; after the 



... ..„drly true, plane, parallel plates of glass were 



cemented on the sides with a mixture of glue and molasses. After a few days 



h-'--' - ^ ing which was then closed 



tttended with a most serious 



a face of a prism thus pre- 

 from it' along the Ixes of the observing telescope, it will 



