OF ARTS AND SCIENCES. 



169 



Professor J. Lovering made a brief communication, describ- 

 ing new experiments and modes of illustrating the laws of 

 Lig'iiT and Sound, 



" 1. At the meeting of the American Association for the Advance- 

 ment of Science, at Cleveland, in August, 1853, I gave an account 

 of some changes, and, as I believed, improvements, in the construc- 

 tion of Soleil's apparatus for projecting on a screen the chromatic 

 phenomena of polarization. As the volume which is to contain the 

 proceedings of that meeting has been unusually delayed in its pub- 

 lication, and has not yet appeared, I propose to present now to the 

 Academy the substance of my former paper. The apparatus of 

 which I speak, as made by Soleil, is described in Pouillet's Traite de 

 Physique, and elsewhere ; and a sectional view of it is given on Plate 

 XXXIV., Fig. 21, of the book first mentioned. I here present the ap- 



Fig. 1. 



kJl 







E 



paratus as I have modified it. Soleil's plan is well adapted to many 

 experiments. If the crystal is small, it is placed near the focus of the 

 large lens, which condenses the light upon it and illuminates it 

 strongly, so that the colored rings, black crosses, &c. developed by 

 the analyzer may be projected upon a distant screen on an enlarged 

 scale. But whenever these experiments are to be repeated with crys- 

 tals of low crystalline power, as quartz, for example, some modifica- 

 tion of the apparatus is necessary. Otherwise, it will be impossible 

 to see anything more than the colored centre without the rings. A 

 more diverging beam of rays is required for the rings. Thus have 

 I been led to the construction of another eyepiece, to be substituted 

 in such cases for that which accompanied the original apparatus. It 

 VOL. III. 22 



