I think New Zealand offers far better chances of success:  it is further from the tropics, it abounds in suitable rivers, the climate and temperature are more like England, and I believe the rivers never degenerate into mere water-holes, as they seem to do in Australia; and I think the residents of that colony ought to make a vigorous attempt to introduce Salmon, Salmon Trout, and the common brown Trout into their rivers immediately; and I should be delighted to render all the assistance in my power to accomplish so desirable an object.

* * * * *

ON THE FORMATION OF ICE AT THE BOTTOM OF RIVERS.

Anchor Frosts.

A correspondent of the “Magazine of Natural History,” in endeavouring to explain the causes why water freezes at the bottom in rapid streams, says this unusual phenomenon may be rationally accounted for by anyone who has attended to it; that the streams in which anchor frosts occur generally are those which contain water of different temperatures—­viz., surface-drainage and land springs and main springs, the first being always colder than the latter, in winter these never being less than 40 degrees, even in severe frosts.

These colder globules being first frozen, float on the surface of the water individually, being prevented from coalescing by the intermediate main-spring-water, and where the water passes in a shallow stream over the pebbles the crystals are intercepted by the interstices of the stones, and then become heaped together in thick beds.

The fact of the crystals of ice (which are specifically lighter than the water) sinking below the surface, is a circumstance requiring explanation.  They do not sink from their specific gravity, but in the commotion of the current they are occasionally submerged, and while so are stopped by any obstruction, when they commence and compose the aggregation.

Thinking this was an erroneous view of the matter, I replied as follows:—­

J. M., in his remarks on anchor frosts, appears to me to have fallen into several errors in endeavouring to account for them (they are called bottom frosts in Yorkshire); for, admitting that main springs are of the temperature stated (40 degrees) when they issue from the earth, I am by no means prepared to believe that they keep that temperature long, or that the water issuing from them does not mingle intimately and immediately with the water of the river into which it flows; especially in the situations where anchor frosts are most common, which are rough and rapid streams.

From J. M.’s statement it would appear that globules of water of different temperatures mix together without the one imparting its excess of caloric to the other, which is contrary to the experience of everyone; it is true, that in still places there will be different temperatures in the same body of water, but it is not owing to the main springs of which J. M. speaks, but to the peculiar way in which water