This book obtaining general approbation, the impression, which consisted of 500 copies, was quickly sold off. A new edition was therefore published, and several others succeeded. Encouraged by this success, he prepared for the press his Three Physico-theological Discourses, concerning the Chaos, Deluge, and Dissolution of the World, the substance of which had been embodied in some sermons which he preached before the university. This work has also gone through several editions. In the opinion of the illustrious Cuvier, it affords "a system of geology as plausible as any of those which had appeared at this period, or for a long time afterwards;" and if it contain facts and arguments which are not now admitted as accurate or conclusive, this, with our experience of like defects in other theories, should teach us to moderate our zeal in defending any hypothesis elicited from the partial examination of that complex system, which, being the work of infinite power and wisdom, cannot be thoroughly understood by minds constituted like ours. In one of these works is an estimate of the number of animals and plants known in Ray's time, to which it is of importance that we should advert, as it furnishes an interesting fact in the history of science. According to the author's classification, animate bodies are divided into four orders, "beasts, birds, fishes, and insects." The number of _beasts_, including also _serpents_, that had been accurately described, he estimates at not above 150, adding that, according to his belief, "not many, that are of any considerable bigness, in the known regions of the world, have escaped the cognizance of the curious." At the present day, more than 1000 species have been described. The number of _birds_, he says, "may be near 500; and the number of _fishes_, secluding shell-fish, as many: but, if the _shell-fish_ be taken in, more than six times the number." As to the species remaining undiscovered, he supposes "the whole sum of beasts and birds to exceed by a third part, and fishes by one-half, those known." The number of _insects_, that is, of animals not included in the above classes, he estimates at 2000 in Britain alone, and 20,000 in the whole world. The number of _plants_ described in Bauhin's Pinax was 6000, and our author supposes, that "there are in the world more than triple that number; there being in the vast continent of America as great a variety of species as with us, and yet but few common to Europe, or perhaps Africk and Asia. And if," says he, "on the other side the equator, there be much land still remaining undiscovered, as probably there may, we must suppose the number of plants to be far greater."--"What," he continues, "can we infer from all this? If the number of creatures be so exceeding great, how great, nay immense, must needs be the power and wisdom of Him who formed them all!"