[94] Savary, Newcomen, Cawley, Watt, and Boulton, Englishmen; and Betancourt and the brothers Perrier, Frenchmen; are names well known in the history of steam-engines. And those persons who wish to acquaint themselves with the principles and manner of operation of this most important class of machines, says Dr. O. Gregory, may be referred to the following work:--The Repertory of Arts and Manufactures, the Philosophical Journal, and the Philosophical Magazine, in various places; the second volume of Mr. Brewster’s edition of Ferguson’s Select Lectures, the second volume of Gregory’s Mechanics, and the second volume of Prony’s treatise entitled Nouvelle Architecture Hydraulique. [95] Plymouth Chronicle. [96] Whitehurst’s Inquiry into the Original State and Formation of the Earth. [97] Examination of Dr. Burnet’s Theory of the Earth, pp. 92, 93. [98] The substances of which vegetables are composed, now amount to fifteen in number; but almost the whole of vegetable substances are composed of four ingredients, namely, carbon, hydrogen, oxygen, and azote. Of these, the last, namely, azote, forms but a small proportion even of those vegetable substances of which it is a constituent part, while, into many, it does not enter at all.--Contemplative Philosopher, vol. i. p. 150. [99] Of the efficacy of water in vegetation, we have on record some remarkable instances. That vegetables will grow in woollen cloth, moss, and in other insoluble media, besides soils provided they be supplied with water, has been repeatedly shown since the days of Van Helmont and Boyle: but the experiments of a modern author, says Mr. Parkes, from their apparent correctness, seem more highly interesting and conclusive.