[BAKNEs] ANCHOR-ICE FORMATION 89 



a paper of M. Arago upon the subject, translated and published in the 

 Edinburgh New Philosophical Journal, vol. xv, p. 123, from the Annu- 

 aire for the year 1833, that he entirely rejects the theory of the radia- 

 tion of heat through a thick la^-^r of water. In the same paper, 

 althougli lie does not, in conclusion, pretend to give a complete explan- 

 ation of the phenomenon, he l)rings forward, as explanations in part, 

 three circumstances, which, although accurately stated by him, appear 

 to be not exclusively appropriate to ice formed at the bottom, and 

 cannot therefore aid us in solving the main question which we have 

 to discuss here, which I apprehend to be. Why is ice formed sometimes 

 on the surface of running ivairr, and, sometiîncs at the bottom? 



On reading M. Arago's paper, T became desirous of offering some 

 remarks in answer to it, as without some one doing this, on proper 

 data, a misapprehension concerning the cause of a natural phenomenon, 

 so much at variance with our most frequent experience of the formation 

 of ice only on the surface of all waters, as to have often greatly excited 

 the attention and even called forth the astonishment of scientific men, 

 would continue to be propagated under the authority of a distinguished 

 name. Having, however, no record of my former observations to enable 

 me to refer accurately to the time, place, and other circumstances of 

 them. T delayed till a renewed occurrence of ice on the bottoms of 

 our streams should enable me to repeat them. 



Such an occurrence, on a great scale, took place in the beginning 

 of this month of January (1835) ; and I now have the honour of pre- 

 senting to the notice of the Eoyal Society a brief account of the 

 observations I have i^een enabled to make, and of the conclusions to 

 which they appear to direct us. 



Previously to entering on this detail and discussion, it seems 

 proper to describe the appearance and quality of the ice fonned at 

 the l)ottoms of streams. A misapprehension regarding these may have 

 been one cause of the incredulity of its existence, entertained by some 

 persons who have never witnessed it, and which ]\I. Arago, in the paper 

 referred to, has deemed it necessary to remove, by bringing forward the 

 testimony of many distinguished men to its reality. 



The ice formed at the bottom does not resemble the solid glass- 

 like plates which are formed on the surface. It has nearly the aspect 

 of the aggregated masses of snow as they are seen floating in rivers 

 fluring a heavy snow shower; but, on taking it out of the water, it 

 is found to be of a much firmer consistence than these, although never 

 approaching to thje firmness and solidity of surface ice. It is a cav- 

 ernous mass of various-sized, ])ut all small, pieces or crystals of ice, 

 adhering together in an apparently irregular manner by their sides. 



