of the receiver. The oil and phlegm descended into the receiver, but
the spirit, still ascending, blew up the bladder. He then filled a good
many bladders with it, and might have filled an inconceivable number more;
for the spirit continued to rise for several hours, and filled the
bladders almost as fast as a man could have blown them with his mouth; and
yet the quantity of coals he distilled was inconsiderable.

"He kept this spirit in the bladders a considerable time, and endeavoured
several ways to condense it, but in vain. And when he wished to amuse his
friends, he would take one of the bladders, and pricking a hole with a
pin, and compressing gently the bladder near the flame of a candle till it
once took fire, it would then continue flaming till all the spirit was
compressed out of the bladder."[1]

The Rev. Stephen Hales, D.D., Rector of Farringdon, Hants, was the author
of a book entitled _Statical Essays, containing Vegetable Staticks_,
printed in 1726-27, and of which the third edition bears the date 1738. At
p. 182 of this work, after a previous description of the destructive
distillation of all kinds of substances in iron or other retorts, he
says--

"By the same means also I found plenty of air [gas] might be obtained from
minerals. Half a cubick inch, or 158 grains of Newcastle coal, yielded in
distillation 180 cubick inches of air [gas], which arose very fast from
the coal, especially while the yellowish fumes ascended."

Still later, viz. about 1767, we have the Rev. R. Watson, D.D., Regius
Professor of Divinity in the University of Cambridge, and Bishop of
Llandaff, interesting himself in chemistry. He wrote a series of
_Chemical Essays_, one of which is entitled, _Of Pit Coal_, and in this he
describes the production from coal (by destructive distillation) of
illuminating gas, ammonia-water, tar, and coke. He further compares the
relative quantities of the different products from various kinds of coal,
but he appears to have been chiefly interested in the tar, and disregarded
the gas and other products. Not the least interesting part of his book is
the preface, in which he apologizes for his pursuits in the following
words--

"Divines, I hope, will forgive me if I have stolen a few hours, not, I
trust, from the duties of my office, but certainly from the studies of my
profession, and employed them in the cultivation of natural philosophy. I
could plead in my defence, the example of some of the gr