242 Intelligence and Miscellaneous Articles. 



anchor ice, are found to accumulate with astonishing rapidity. These 

 accumulations of ice, by damming up the water, cause great floods, 

 and by yielding to the force of the water, and moving down with 

 the current, especially after they have become jammed and heaped up 

 with other ice formed on the surface, act in producing very striking 

 geological effects in disturbing the bottom and banks of the river, 

 and in shoving along huge boulders which otherwise would remain 

 immoveable. The ground- and surface-ice, also, by their shoving- 

 action, introduce formidable difficulties and dangers in the construc- 

 tion of bridges or other engineering works requiring to be founded 

 on the beds of rivers in cold climates. In the construction of the 

 Great Victoria Bridge across the St. Lawrence at Montreal (the most 

 costly bridge which has ever been executed), these difficulties have 

 been successfully overcome, and a structure has been raised which is 

 likely to stand secure against the much- dreaded forces of the ice. On 

 account of the tendency both of water approaching to the freezing- 

 point and of ice to float, it has long been regarded as rather a singular 

 circumstance that ice should ever be found growing at the bottom 

 of a river. From among the many suggestions which have been 

 offered at various times to account more or less completely for the 

 phenomenon, the author sets out by accepting as quite correct the 

 view that the essential difference between the circumstances of the 

 freezing of lake and river water is, that in the former case the water 

 is left undisturbed to the action of the cold, and is allowed to adjust 

 itself in strata in which the coldest parts, being also the lightest, float 

 to the top ; while in rivers the whole water is, by mixing, due to its 

 rapid flow, brought to a uniform temperature at the freezing-point 

 from top to bottom, and is thus brought into a condition in which it 

 is ready to freeze at any part where additional cold may be applied. 

 He is not, however, satisfied with any of the numerous suggestions 

 which have been offered to account for the growth of the masses of 

 spongy ice at the bottom, rather than that the ice should be found 

 at the top, or in a state of mixture with the water throughout its 

 depth. Some, for instance, have thought that radiation from the 

 bottom to a cold sky (see paper by the Rev. James Farquharson, 

 Philosophical Transactions, 1835) would cause ice to grow at the 

 bottom of the river much in the same way as hoar-frost grows on 

 land. Arago, having rejected the supposition of radiation being the 

 cause, assigned two other reasons : first, that there might be expected 

 to be a peculiar aptitude to the formation of crystals on the stones 

 and asperities at the bottom, like as there is found to be a special 

 readiness for the formation of crystals on rough bodies in saline solu- 

 tions ; and secondly, he supposed that the existence of less motion of 

 the water at the bottom would favour the growth of the crystals 

 there. As against this view, the author of the present paper states, 

 first, that the water of a rapid river when freezing has abundance of 

 small spicula or fragments of ice floating diffused through it, every 

 one of which offers at least as free a point for the reception of new 

 ice crystallizing from the water as can be presented by asperities on 

 the bottom ; and secondly, that the slower motion at the bottom 



