It is in vain to endeavour to shew that opportunities for the transmission of contagious atmosphere have not occurred. The case involves an impossibility, for do not a thousand means of communication suggest themselves to the mind of the reader? The atmosphere itself, currents, winds, water, streams, &c.,—animals,—such as rats, mice, winged insects, &c. &c., which cannot be prevented from operating. We, therefore, leave this case, perhaps to the efforts of the advocates of quarantine regulations, who possibly may arrive at a happier result, and we proceed to the opposite case, where disease fails to spread, where communication does take place. The advocates of contagion prove, where a disease appears in a town, that communication has taken place. That statement, as the reverse, can never be proven, is easily affirmed; and its insignificance corresponds with the facility with which it can be proven. Of course, it is obvious, that such a fact proves very little, either in reference to contagion or anything else. We are prepared to prove, that communication has subsisted on many different occasions, without any unusual amount of sickness taking place. We know of many instances where disease has been prevailing in a town or village, which has failed to manifest itself in another at a short distance, although daily unrestrained communication was held. At the end of the year 1835, and the beginning of the year 1836 the scarlet fever prevailed in Edinburgh to a great extent; and although great traffic was constantly going on between that town and Tranent, by means of foot-passengers, numerous carts and coaches, passing to and fro, daily, still that distemper failed to make its appearance in the latter town till the 20th of January, the day on which the first case was noticed. That case did not occur at the point where the greatest thoroughfare subsists, but at one, the most remote from it. Typhus fever has been prevailing, to a great extent, in Edinburgh, for many weeks past, but that disease has failed to make its appearance in Tranent (ten miles distant), although the road is constantly crowded with carriages, with vast numbers of carts conveying coals from that village to the capital, and with passengers both on horse and foot. It has not made its appearance, although several of the inhabitants of Tranent have lately lost relatives who have died of that disease, both in Edinburgh and Leith; and although a woman just recovered from that distemper, and come from the Royal Infirmary, has taken up her abode in this village. Small-pox appeared about six weeks ago, simultaneously in two very filthy localities in Tranent, and it has been confined to them, although the most free communication has subsisted with other parts of the village, and it has failed to spread to the hamlets and farm-steadings around, notwithstanding the relatives of some of those labouring under that disease have travelled through the country, seeking charity.