FACTS AND OBSERVATIONS. 
405 
however^ far surpass in extent and interest all previous disco¬ 
veries ; and the quantity already yielded^ without apparently 
diminishing the supply^ show^s that this will be a most im¬ 
portant article of commerce for some years to come. In 
Canada the oil rises from the saturated corniferous lime¬ 
stones ; in the States it is principally obtained from Devonian 
sandstones, while in Western Virginia and Ohio it rises 
directly from the coal-measures. In all cases it no doubt 
arises from the decomposition of coal by temperature and 
pressure, and is lifted by the percolation of water under it to 
cavities and fissures in rocks till it approaches the surface. 
It is generally accompanied by quantities of coal-gas. 
Ergot of Wheat. — M. Leperdriel has proposed the em¬ 
ployment of ergot of wheat as a substitute for that of rye. 
The reasons for which, as assigned by him, are, 1st, it does 
not undergo decay or change very quickly. 2nd, it con¬ 
tains 15 per cent, less of the poisonous resinous principle, 
and 20 per cent, more of the efficacious principle of the 
ergots. 
Although ergot of wheat is less frequently met with than 
that of rye, nevertheless M. Tulause says it is not so difficult 
to obtain as many authors suppose. It is produced mostly in 
wet seasons, and always on that side of the ear exposed to 
damp. 
Professor Bentley concurs in the long retention of the 
virtues of the ergot of wheat, as stated by M. Leperdriel; 
but he seems inclined to question its greater efficacy over 
that of rye; nevertheless, he thinks the profession would do 
well to subject them both to comparative experiments. He 
says that some years since it was tried with success in North 
America, and it seems probable that the ergot of all grasses 
possessed analogous properties. 
Application of Dialysis. —This ingenious mode of sepa¬ 
rating substances, to which we alluded in a former volume, 
has been applied by Dr. Marcet for separating the salt from 
the juice of meat in brine. Large quantities of brine are 
Avasted in curing establishments, and it is proposed that the 
juice of the meat, containing as it is known to do much 
nutritive matter, shall be used as an article of diet. 
Professor Williamson, in a debate on the use of dialysis in 
microscopical observations, indicated a number of subjects 
on Avhich he thought it probable that some light Avould be 
thrown both in vegetable and animal physiology, especially 
as seen in the development of the dental plates of the teeth 
xxxvi. 27 
