NOVELTIES. 



143 



direct to the right eye, the right half being collected by the 

 prism and refracted to the left eye. 



The Pseudo-Binocular Prism has, however, five surfaces, (the 

 emergent surface being also made twice the ordinary width). Be- 

 yond the usual base, another surface is added, ground parallel with the 

 emergent surface, thus allowing light to pass directly through the 

 prism at this point. As a binocular, the prism would be used in 

 the usual manner, the ordinary base occupying the right half of 

 the field, and refracting the collected rays to the left eye. By 

 pushing the prism in so that it occupies the whole of the field, its 

 action is reversed, the left half of the rays being refracted to the 

 left eye ; the right half passing through the parallel surfaces of 

 prism to the right eye, the effect being to instantaneously invert the 

 imao-e, a convex surface presenting a concave appearance and vice 

 versa. This ingenious modification of Mr. Wenham's prism is the 

 invention of Mr. Ahrens ; its construction does not in any way 

 affect the performance of the instrument as an ordinary binocular, 

 at the same time illustrating one of the most curious optical phe- 

 nomena. 



New Syphon Collecting Bottle, with Dipping Case. — We 

 are indebted to Mr. George for another collecting bottle, which he 

 has named as above, and of which we give a cut. It consists of a 



Fig. 1. 



Fig. 2. 



bottle. A, fig. 1, stopped by a plug, B, over which is'stretched a ring 

 of India-rubber, and into which is soldered the funnel, C, and the 

 sy|Dhontube, E, to which is attached the strainer, D ; F is a flexible 

 tube, with a plug attached, to be turned over to stop the mouth of 



