The importance of experiments and investigations such as those recorded by the Rev. J. D. La Touche, in the Geological Magazine for April, can hardly be over-estimated from a geological point of view, and, if carried on in numerous districts and for a sufficient length of time, would furnish data with which, and a basis from which, future calculations as to the rate of denudation at present going on over the land surface of the globe might be esti- mated. For it cannot be denied that at present there is a laxness in the method of computation as regards the rate and amount of degradation both for past and present epochs which ill accords with the ultimate end and aim of all scientific pursuits, viz., truth. Each one taking a rate which seems most to confirm his own particular tenets, as, for instance, the different rates at which the river Niagara has out its way back from Queenstown Heights to the present situa- tion of the Tails. It has been taken as three feet, one foot, six inches, and one inch per annum, by different computators. Now I do not say that investigations on the river action of the period in which we live will clear up all such anomalies, because these obser- vations will be of more service in estimating the future rate of the wearing down of the materials composing the land than that of the past, as there would always be the difficulty of ascertaining with precision the volume and velocity of the rivers, and the different elevations at which the land was situated at the particular era under consideration; still it would be a fulcrum on which we might rest the lever of analogy, and raise many questions at present resting in obscurity and doubt into light and certainty.