400 



Scientific Intelligence. 



south end as it lay originally). Most of these I presume are 

 simply the marks of vehicles, which, for the whole spring, passed 

 over this part of the bowlder, and I was surprised to find that 

 they made so slight an impression. I think, however, that 

 among these wagon tracks I can see one or two produced by 

 some other agency ; and it is not improbable that during its 

 rough transportation, bowlders might have been forced over it 

 in that direction. 



I have regarded the detritus collected along the central part 

 of Amherst, where this bowlder lay, as Modified Drift : that is, 

 coarse drift that has been subsequently acted upon, and more or 

 less rounded and sorted by water. Generally the fragments at 

 this place are more rounded and of less size than we see in the 

 coarse drift upon the neighboring hills, and yet the bowlders are 

 considerably larger, though the one now described is much the 

 largest I have seen in our modified drift. 



As this bowlder seems to me to be of unusual interest, and 

 is now placed permanently, through the energy and scientific 

 zeal of the class of 1857, where geologists can examine it, I have 

 thought this description might be acceptable to the readers of the 

 Journal. At any rate, it has been the means of qualifying one 

 College Class, as they wander over the world, to examine stri- 

 ated bowlders and ledges. 



SCIENTIFIC INTELLIGENCE. 



I. CHEMISTRY AND PHYSICS. 



1. On the wave lengths of the most refrangible rays of light in the In- 

 terference Spectrum. — Eisenlohr has contributed a very interesting paper 

 upon the wave lengths of the invisible rays, which he has determined by 

 means of the diffraction spectrum, essentially in the manner employed by 

 Schwerd. The author in the first place describes his method of project- 

 ing the phenomena of diffraction upon a screen. A ray of light is intro- 

 duced horizontally into a dark room by means of a heliostat and allowed 

 to fall upon a narrow vertical slit or other opening placed at a distance of 

 one meter. From 4 to 12 meters behind this slit an achromatic object- 

 glass of 3 meters focal length is placed in a round hole in a board, the 

 plane of which is at right angles to the incident ray. Disks with 

 lattices of different kinds may be fastened immediately in front of the 

 object-glass ; a white or transparent screen is placed at a proper dis- 

 tance behind the lens. The image of the slit must be distinctly projected 

 upon this screen before the lattice is fastened in front of the object-glass. 

 In this manner, spectra of extraordinary size and beauty are obtained, 

 particularly when the openings are very narrow and numerous. All the 

 phenomena of diffraction described by Schwerd in his classical work may 

 in this way be represented so that they may be seen by a number of 



