On the whole, we regard this document as decidedly confirmatory of the views which have been uniformly advocated by the Philadelphia Society for the Alleviation of the Miseries of Public Prisons, and in the pages of this Journal. It contains not a statement nor a tittle of evidence that impairs in the slightest degree our confidence in the safety, efficacy and humanity of convict-separation. That it has been, and may be abused or ill-administered, and that it requires judgment and discrimination to adapt its provisions to the various classes of persons who are subjected to it, is not more true of this than it is of the gregarious or any other system. The only substantial fault that we have ever known to be found with it, is that it costs more than association, and the only answer to be made to this is, that (admitting the statement to be true) it is worth as much more as it costs. ART. III.--SOURCES AND CHECKS OF JUVENILE DELINQUENCY. When the farmer finds his fruit trees exposed to the ravages of the caterpillar, he makes but slow and unsatisfactory work, if he takes the worms one by one as they are feasting on the leaf, or crawling along the stem, or dangling in the air. There is a period of the day, however, when they are all in their nest, and if he can apply a torch to their curious fabric and consume it, or riddle it with shot, or wind it and its wriggling population upon a brush or broom well besmeared with pitch or tar, to be forthwith put into the fire or under the foot, the work is thorough and the tree safe. Not inaptly does this illustrate, or serve to point out the true process for the diminution of crime. The arrest, conviction and punishment of here and there a rogue, is scarcely felt. It is but a unit subtracted from the appalling aggregate of crime. If we would have the ratio of our criminal population palpably and permanently lessened, we must lay hold of the young ones in the nest, and whatever the trouble or cost, we may rest assured it is by all odds the cheapest and only effectual way of dealing with the pest. Among the prominent causes of, or excitements to a criminal life which are operative upon childhood, especially in cities and populous towns, have been reckoned 1, and chiefly drunkenness. 2. The absence of education and industrial training. 3. The inadequacy of home-accommodation to secure the ordinary decencies of life. 4. The demoralizing influences of cheap theatres, and other low places of amusement, association with fire companies, and the liberty to dispose of the whole or a considerable portion of their own earnings. 5. The example, instruction or orders of parents constraining them to vicious acts, and 6, the connivance or co-operation of receivers of stolen goods to prompt them. We might indefinitely enlarge this catalogue, but these causes are adequate to account for the greater part of juvenile crime.