322 GROUND OR ANCHOR ICE. 
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 would not favour the ee eee of freezing of new 
ice there rather than at the top, but that, on the contrary, if effects on the tend- 
ency to crystallization are to be sought for in such a slight cause, it should 
rather be taken that the greater fluid friction at the bottom, and the heavier 
pressure there, are causes slightly, but certainly very slightly, tending to oppose 
the freezing of new ice at the bottom. 
Mr. Hodges, the engineer of the contractors for the great bridge across the 
St. Lawrence at Montreal, in his large and valuable work recently published (in 
1860) on the construction of that bridge, describes the ice-phenomena of the 
St. Lawrence, which he had been obliged during many years to watch and 
inquire into with anxious care; and in respect to the origin of the ground-ice, 
he supposes that the water in passing down rapids may become aerated by the 
‘rapidity of the current, and that particles or globules of cold air, being whirled 
by the eddies till they come in contact with the rocky bed of the river, attach 
themselves to it, and there give out cold which they have brought with them 
from the very cold atmosphere above, and so induce the freezing of ice around 
themselves in adhesion to the bottom of the river. As against this speculation, 
the author of the present paper states that the cold which could be conveyed 
down into the water by small bubbles would be totally inadequate to produce 
the results in question, and that any freezing which small bubbles of air could 
produce would occur during the period of their eddying about through the 
water, rather than at a later time, when their temperature would be assimilated 
to that of the water. The author's view, which it was the chief object of the 
paper to present, is that crystals or small pieces of ice are frozen from the 
water at any part of the depth of the stream, whether the top, the middle, or 
the bottom, where cold may be introduced either by contact or radiation, and 
that they may be supplied in part by snow or otherwise; and that they are 
whirled about in currents and eddies until they come in contact with any fixed 
objects to which they can adhere, and which may perhaps be rocks or stones, or 
may be pieces of ice accidentally caught in crevices of the rocks or stones, or 
may be ground-ice already grown from sucha beginning. The growth of the 
ice by adhesion of new particles formed elsewhere he attributes to the property 
of any two pieces of moist ice to adhere when brought into contact, whch has 
been a subject of much discussion of late years, and of which the author’s views 
are to be found in various recent papers in the ‘Proceedings of the Royal 
Society,’ and have also been submitted from time to time to the Belfast Natural 
History and Philosophical Society. He is confident that the anchor ice is not 
formed by crystallization at the place where it is found adhering. He is aware 
that the idea has sometimes been mooted, that snow falling into rivers might 
somehow be converted into anchor ice; but he is not aware that hitherto any 
explanation has been offered coupling the formation of the anchor ice with the 
property of ice now commonly designated as “‘ regelation,” but which until late 
years was not very generally known or understood, more especially as a pro- 
