By physicians of the first eminence, such occurrences as that referred to in connection with the Royal Infirmary of Edinburgh, are held as decisive proof of the operation of contagious atmosphere. Dr Alexander Tweedie, a physician of London, and one justly eminent, after mentioning the self-same cause, goes on to say, in a sufficiently assured tone,—“No statement more conclusive, as to the contagious nature of fever, need be adduced: and if such facts will not lead to conviction, the mind of such a sceptic must be strangely constructed indeed.” The case had been made much stronger, and would have stood inquiry much better, had Dr Tweedie shewn, that the occurrence he treats of was not solitary or uncommon, but was such as is wont to be observed in all like institutions. He should have known, that it is not from extraordinary, nor even from unique cases alone, that knowledge is to be obtained, nor laws deduced, of the ordinary characters, and action of disease. It is dangerous to deduce inferences, and construct laws, from the knowledge of one circumstance, and where, too, many can be obtained bearing on the case. Let us see if this occurrence holds with other establishments. We will find that it by no means always holds. Dr Bateman, who saw much of fever, and gave it much of his active consideration, in his excellent Treatise on Contagious Fever, says,—“During the fourteen years, in the course of which I have almost daily been in contact with persons labouring under contagious fever, not only myself, but all the nurses have been preserved from infection, with one exception, down to the period of the present epidemic” (in the London House of Recovery).[3] Footnote 3: Bateman on Contagious Fever, p. 154. 1818. Similar cases of exemption might be given, but it seems unnecessary to say more here. But though Dr Bateman’s evidence in a manner meets the case recorded, connected with the Royal Infirmary of Edinburgh, yet it does not disprove its correctness; and we proceed to explain what has been held as only to be explained by the presence of atmospheric contagion. But though the case could not at present be explained, we deny that one such circumstantial piece of evidence should outweigh the many facts, and the results of reasoning, that have been laid before the reader, and that are yet to follow. When evidence is contradictory, it is well to ascertain on which side it preponderates; and even when it is nicely balanced, which is not the case here, it should be tested by a reference to general principles. That was done in the first part of this work, and the reader cannot have forgotten the result.