FARQUHARSON ON FORMATION OF GROUND ICE. 353 



Physiques,"" (Paris, 1 866), of an essay by Engelhardt, whose observations 

 were made on the lower Rhine. From this we learn that the first men- 

 tion made of ground-ice by any writer is by Dr. Plott, in 1705, in his 

 "Natural History of Oxfordshire." 



Arago, in the "Annuaire du Bureau des Longitudes" for 1833, first 

 gave the proper explanation of the formation of ground ice ; this expla- 

 nation Engelhardt adopts with an addition. " With Arago, then," he 

 says, "I attribute the formation of ice at the bottom of water princi- 

 pally to the obstacles which occur in the current ; but, in my view, 

 these obstacles are not solely resting" points for the crystals, but they 

 serve, on tlie one hand, to augment the movement of rotation, the vor- 

 tiginous movement by which the water at a temperature 0" C. (30oF.) is 

 made to descend to the bottom of the river ; and, on the other hand, they 

 create stationary points in the midst of the movement, when the crystal- 

 izing force can exert itself." 



Another article on the subject is a notice in the Journal of Applied 

 Science, of a paper by Professor Hind, of New Brunswick, giving some 

 account of the effects of anchor ice on the coast of Newfoundland. 

 He speaks of the anchor ice forming about the seal-nets, at the depth 

 of from 50 to 61) feet below the surface, and that if the sealers neglect to 

 lift the nets after spiculse of ice begin to form on the casks at this depth, 

 they are liable to be lifted by the forming ice, and being carried away 

 by the tides are lost. This autlioi on the authority of Despretz, explains 

 the phenomenon by the statement that sea-water, when near the freez- 

 ing point, behaves differently from fresh water ; taking no account of 

 the mixing of the surface water with that below, by the action of the 

 tides, the rougliness of the bottom, &c. It is very doubtful if sea water 

 in cooling obeys a different law from fresh water, for it has been lately 

 shown that all the metals and sonie rocks expand or become of less spe- 

 cific gravity at the moment of solidification or freezing, a property long 

 known as belonging to, and thought also to be peculiar to some of the 

 more easily fusibln metals; indeed, it would seem highly probable that 

 all bodies obeyed the uniform law that all bodies are lighter in the solid 

 than in the fluid state, that all solids would float on the surface of their 

 liquids, just as ice floats in water. But, there is no necessity in calling 

 in the aid of any supposed peculiarity of salt water, when almost identi- 

 cally the same phenomena are to be seen in fresh water. 



Anchor or ground-ice forms upon the chain cables of vessels anchor- 

 ing in the Detroit river to the depth of fifty feet and more. Some 

 years ago, the apparatus for straining the water at the mouth of the 

 conduit, which supplies the city of Detroit with water, which was in 

 very deep water, and projected somewhat above tlie bottom, became so 

 covered with ground-ice, as to completely stop the flow of the water, 

 and necessitate its removal. The divers engaged in this work could see 

 the whole mass of water filled with spiculae or crystals of ice, wliich 

 needed but the momentary check of the current by some obstacle to 

 form a spongy mass of ice. Here the cooling of this great mass of wate*' 



