But the decomposition of animal bodies is remarkably modified by external circumstances where the bodies are immersed in or surrounded by water, and particularly, if the water undergo frequent change, the solid tissues become converted into adipocire, a fatty spermaceti-like substance, not very prone to decomposition, and this change is effected without much gaseous exhalation. Under such circumstances nothing injurious could arise, but under ordinary conditions slow decomposition would take place, with the usual products of the decomposition of animal matters, and here the nature of the soil becomes of much interest. If the burial-ground be in damp dense compact clay, with much water, the water will collect round the body, and there will be a disposition to the formation of adipocire, whilst the clay will effectually prevent the escape of gaseous matter. If on the other hand the bodies be laid in sand or gravel, decomposition will readily take place, the gases will easily permeate the superjacent soil and escape into the atmosphere, and this with a facility which may be judged of when the fact is stated, that under a pressure of only three-fourths of an inch of water, coal gas will escape by any leakage in the conduit pipes through a stratum of sand or gravel of three feet in thickness in an exceedingly short space of time. The three feet of soil seems to oppose scarcely any resistance to its passage to the surface; but if the joints of the pipes be enveloped by a thin layer of clay, the escape is effectually prevented. If bodies were interred eight or ten feet deep in sandy or gravelly soils, I am convinced little would be gained by it; the gases would find a ready exit from almost any practicable depth. § 22. He also expresses an opinion concurrent with that of other physiologists, that the effects of these escapes in an otherwise salubrious locality, soon attract notice, but their influence in obedience to the laws of gaseous diffusion, developed by Dalton and Graham, is not the less when scattered over a town, because in a multitude of scents they escape observation. In open rural districts these gases soon intermix with the circumambient air, and become so vastly diluted that their injurious tendency is less potent. Other physical facts which it is necessary to develope in respect to the practice of interment may be the most conveniently considered in a subsequent portion of this report, where it is necessary to adduce the information possessed, as to the sites of places of burial, and the sanitary precautions necessary in respect to them. § 23. From what has already been adduced, it may here be stated as a conclusion,