200 G. Thibaut — On the S'ulvasutras. [Nov. 



wbile tbe lines stand out clearly, though not in very good definition owing 

 to my having used a rather large opening of the slit. 



It will he observed also that the part of the spectrum acted upon by 

 the blue and violet rays is also reversed, so that the whole spectrum is re- 

 versed from a little above H2 to below A. This action I have noticed on 

 all dry bromide plates, both stained and unstained, and have frequently 

 obtained very beautiful images of the lines between H2 and F on a per- 

 fectly clear ground. The effect appears to be chiefly caused by overexposure 

 and may perhaps be partly due to the action of the alkaline developer. 



As above stated, the reversing action of the red rays has been observed 

 with daguerreotype plates and therefore I cannot claim to have made a 

 discovery, but so far as I am aware the application of the principle to collo- 

 dion photography is entirely new, and as it appears capable of an important 

 practical application in spectroscopic photography, particularly in extending 

 our knowledge of a part of the spectrum in which eye-observations can only 

 be made with difficulty and under very favourable circumstances, I have 

 thought it worth bringing to the notice of the Society and hope to be able 

 to continue the investigations with still better results.. 



Capt. Waterhouse further remarked that these photographs had an 

 additional interest from the fact that the lines in the extreme red had 

 hitherto only been observed about sunrise and sunset and that according to 

 Mr. J. B. N. Hennessey, who had made a very careful study of them at 

 Mussooree in 1870, complete darkness prevailed at sun-high in the part 

 of the spectrum in which they are situated. The photograph, however, 

 which shows the lines with most distinctness was taken between 1 and 

 2 P. M. and the spectrum extends to a distance below A equal. to that of the 

 line C above it, or very considerably beyond the limits of Mr. Hennessey's 

 map and of the earlier ones by Brewster and Gladstone. 



The following papers were read : — 



1. On the S'ulvasutras ; or Notes on the beginning of Geometry in India. — 

 By Dr. G. Thibaut, Anglo- Sanskrit Professor, Bandras College. 



(Abstract.) 



This paper, a portion of which was read by Dr. Thibaut at the last 

 Oriental Congress, has been printed with numerous diagrams in No. Ill of 

 Pfc. I, of this year's Journal. Dr. Thibaut has published several of the 

 S'ulvasutras in the Banaras " Pandit." 



Extracts from the paper were read by the Secretary. 



2. On a new species of Tupistra from Upper Tenasserim. — By S. Ktjrz. 



(Abstract.) 

 In this paper the author describes a second species of Tupistra 

 under the name of F. Stoliczkana. It is one of the numerous valuable 



