306 Scientific Intelligence^ ^"c. 



has found means of placing thermometers in a colliery at Bedminstcr, 

 near Bristol. The results confirm the alleged increase of tempera- 

 ture beneath the surface. In one instance, the instrument stood at 

 78 degrees constantly, whilst the mean temperature of the air above 

 was 47 degrees. 



7. Mr. Craig read a paper on Polarization, with a view to 

 show that the phenomena are referable to the division and conse- 

 quently to the weakening of the impulse of light ; and the inability, 

 therefore, to pass through other regular structures without ex- 

 hibiting phenomena which arise out of the peculiarites of such 

 structures. 



Tuesday, 23r^ Atigust — 1. 3fr. Russell on the Phenomena of 

 Waves. — Mr. R. states that, in the course of his experiments on 

 this interesting subject, he finds many different classes of waves 

 obeying different laws. He has observed principally four classes ; 

 1st, the simple ripple, which is not propagated beyond the point of 

 generation ; 2nd, oscillatory waves, such as are produced by a stone 

 dropped into water ; these are propagated with a velocity dependent 

 on the magnitude of the displaced fluid; 3rd, waves having a broken 

 top, called surges ; 4th, the single, solitary wave, which is propa- 

 gated with a nearly uniform velocity. The two last classes are those 

 which had been principally investigated by Mr. Russell : 1st, it 

 ^vas observed that when any addition is made to a quiescent fluid, an 

 elevation is propagated along its surface with a velocity equal to that 

 which would be required by falling through half the depth of the 

 fluid ; 2nd, that the height of such wave is to be added to the depth, 

 in order that the law may express accurately the velocity ; 3rd, that 

 the length of the wave is closely connected with the depth of the 

 fluid; 4th, that it varies with the height; 5th, that when the 

 height of the wave is nearly equal to the depth of the quiescent 

 fluid, the wave breaks ; (3th, by a canal of variable depth the 

 deviation of surges or waves is explained, and also the formation of 

 a tide bore ; 7th, the phenomena of weaves observed in a canal which 

 gradually diminishes in breadth, are analogous to the phenomenon 

 of the extremely high tides observed in narrow rivers and channels. 



2. Mr. Powell on Refractive Indices. — The determination of 

 the refractive indices for definite rays of the solar spectrum, marked 

 by the dark lines, from the direct observation of their deviations 

 produced by prisms of different substances, first proposed and exe- 

 cuted by Fraunhofer, for ten media solid and fluid, was carried on 

 by M. Rudberg for ten more cases. The necessity of an extended 

 series of such determinations was pointed out by Sir J. Herschell 

 and Sir D. Brewster, and was further urged by a special recommen- 

 dation of the British Association. Mr. Powell, by a simple and 

 most ingenious apparatus, has ascertained the refractive indices 

 belonging to each of the standard primary rays for various media, 

 which may be considered as a most valuable contribution to this 

 branch of science. 



3. Sir David Brewster on the Polarizing Structure of the 

 Crystalline Lens, of the eyes of Animals after Death. — These 

 inquiries, which form the subject of this paper, were made by com- 



