160 ANNUAL OF SCIENTIFIC DISCOVERY. 



these experiments it follows, that the phenomenon of the longitudinal 

 lines is not peculiar to the spectrum, but that in every case lines of 

 interference must exist in light which has passed through a convex 

 lens. 



I therefore removed the prism, and made the slit in the window- 

 shutter wider. White light now passed through the lens. By mov- 

 ing the plane of projection backwards and forwards, a position was at 

 length found where the whole breadth of the white image was inter- 

 sected by splendid black lines which crossed it horizontally. 



It is scarcely necessary to remark, that I made many experiments 

 to convince myself, that in the production of these lines, no foreign 

 influences come into play, which, however, is sufficiently proved by 

 the mere inspection of them. 



METHOD BY WHICH THE EYE JUDGES OF DISTANCES. 



The London Art Journal says, that many opinions have been at 

 various times advanced relative to the determination of proximity or 

 remoteness of objects from the eye, but the most plausible hypothesis 

 seemed to be that some time ago suggested by Hermann Meyer, of 

 Zurich, namely, that proximity of an object was determined by di- 

 vergence of the two optic axes. The reflective stereoscope has de- 

 monstrated the correctness of M. Meyer's hypothesis. If after having ' 

 placed the two pictures in the stereoscope in such a manner that their 

 centers correspond, and when, consequently, one single image in re- 

 lief appears, the two designs be drawn simultaneously towards the 

 eyes, the dimensions of the image in relief seem to grow less. If, 

 however, the two designs be simultaneously removed from the eyes, 

 then the image in relief seems to grow smaller than before. Now it 

 is obvious that the convergence of the two optic axes increases in 

 proportion as the two screens are brought near to the eyes, and de- 

 creases in proportion as they are removed. 



NEW PHOTOMETER. 



At the last meeting of the British Association, Dr. Price exhibited 

 the plan of a new photometer. The author, by arranging two in- 

 clined mirrors in a box, contrived to reflect the standard light and 

 the light to be measured, so as to cross each other at a piece of ground 

 glass or oiled paper on the top of the box ; then it was easy, he assert- 

 ed, to adjust the distance of the standard light so as to make the two 

 reflected lights appear equally intense, and then, on the common 

 principle, the illuminating power of the light to be estimated could be 

 calculated. 



CURIOUS OPTICAL PHENOMENON. 



A work of art illustrating a curious optical phenomenon, has been 

 recently exhibited at Cologne, Germany. It consists of a flat surface 



