1072 Teaxsacttoxs of the Amebic ax Ixstitvtb. 



various media is independent of their refractive power. This fact 

 furnislied a clue to the solution of the problem of removing the 

 coloration of bodies in the use of lenees. Flint glass has a greater 

 refractive poAver than crown glass. If a lens of flint glass and a lens 

 of crown glass be placed together, the curvature of each may be 

 such that the dispersive power of each may be destroyed, v/hile a 

 part of the refractive power is retained. 



Researches into the spectrum show that differently colored lights 

 have different degrees of velocity. A difference between various 

 matters is also observable in this resjiect. Some substances will only 

 transmit rays of a certain velocity, while other media will allow rays 

 of a different velocity to pass through them. Rock salt will transmit, 

 rays of a lower velocity than glass. Rays, therefore, which are not 

 visible to the eye, or rays of heat, will pass through this medium 

 which rays of light can scarcely penetrate. We are thus enabled to 

 liave a heat spectrum. The chemical rays of the spectrum may also 

 be separated. Dr. Yanderweyde finally spoke of the great advances 

 which have been made in the microscope, claiming that much is yet 

 to be done in this field. 



Experiments with LrMiNous Flames. 



Mr. John Johnson then exhibited an apparatus designed to 

 demonstrate that flames are composed of cones of different colors. 

 The apparatus consisted of a long tube connected with the gas pipe 

 by an India rubber tube ; a small flame of gas may thus be obtained 

 at the end of the tube. By shaking this tube violently around, the 

 colors of the spectrum are to be observed in the flame. Mr. John- 

 son also explained a means for utilizing smoky hydro-carbon oils. 

 The burning oils were placed under a Bunscn burner open at the 

 bottom. The almost colorless flame of the burner was thereby ren- 

 dered very bright, the unconsumed particles of carbon from the oil 

 becoming incandescent in the Bunsen flame. • ■ 



The society then adjourned. 



April 29th, 1869. 



Professor S. D. Tillman in the chair. I^Ir. C. E. Stetson, Secretary. 



Dr. Tillman read the following interesting paper upon a subject 

 which is at present attracting a good deal of attention : 



