Intelligence and Miscellaneous Articles. 247 



of a uranium glass, the solar light which illuminates the slit of the 

 collimator. 



Such are the phenomena which for the last two years I have studied 

 whenever the sun allows. I am now in a position to enable members 

 of the Academy interested in the phenomenon to witness it. — 

 Comptes Rendus, July 21, 1862. 



ON THE CALM LINES OFTEN SEEN ON A RIPPLED SEA. 

 BY PROFESSOR JAMES THOMSON. 



In this paper the object of the author was to offer a new explana- 

 tion of the origin of lines of glassy-calm water, usually long and 

 sinuous, which are often to be seen extending over the surface of a 

 sea darkened elsewhere by a ripple. He adverted to the commonly 

 received supposition that these lines are due to some kind of oily 

 film on the surface of the water, and to the prevalent idea that the 

 oil is somehow given off from shoals of fishes. These suppositions, 

 he thought, although having some slight foundation in the facts of 

 the case, did not form the true explanation of the phenomenon. 

 His brother, Professor William Thomson, had observed, and had 

 pointed out to him, that the water at the calm lines always contains 

 considerable quantities of small floating objects, such as little detached 

 pieces of seaweed, leaves of trees, or the like, and had accounted for 

 the smoothness of the water by the friction induced among the little 

 undulations by the presence of those solid objects. The question 

 still remained, however, as to what might be the cause of the leaves 

 and seaweed being arranged in such long and sinuous lines. One 

 of these calm lines was noticed last autumn in Brodick Bay by 

 Professor William Thomson and the author ; and on rowing into 

 it, they found leaves and seaweed abundantly diffused through the 

 water there, while the rippled water on both sides of it was com- 

 paratively free from such objects. The line of calm water evidently 

 sprang from a point on the shore where a small river entered the sea, 

 and there could be no doubt that the leaves were supplied by that 

 river. Still it appeared an untenable supposition that the river 

 water could extend so very far out to >jea, and wind about over the 

 surface of the sea as the calm line did, sometimes even narrowing 

 instead of spreading out as a broad sheet, which the light fresh water 

 flowing over the heavy salt w r ater should be expected to do. It 

 occurred to the author that the water of the river would actually 

 spread out as a broad sheet over the surface of the sea ; and that in 

 its outward lateral flow it would constantly be carrying with it the 

 leaves with which it was originally charged, and all such small pieces 

 of seaweed as it might meet with in the sea- water, and that these 

 would accumulate in a boundary line of the region of dispersion, 

 which might be determined by some slight flow of the surface of the 

 adjacent sea-water meeting this outspreading fresher water, and 

 causing a downward or sinking motion, however slight, of the two 



