[18] The engine at Huel Towan. See Mr. Henwood’s Statement “of the performance of steam-engines in Cornwall for April, May, and June, 1829.” Brewster’s Journal, Oct. 1829.--The _highest_ monthly average of this engine extends to 79 millions of pounds. [19] However, this is not quite a fair statement; a man’s daily labour is about 4 lbs. of coals. The extreme toil of this ascent arises from other obvious causes than the mere height. [20] Its surface is about 40,000 acres, and medium depth about 20 feet. It was proposed to drain it by running embankments across it, and thus cutting it up into more manageable portions to be drained by windmills. [21] No one doubts the _practicability_ of the undertaking. Eight or nine thousand chaldrons of coals duly burnt would evacuate the whole contents. But many doubt whether it would be profitable, and some, considering that a few hundreds of fishermen who gain their livelihood on its waters would be dispossessed, deny that it would be _desirable_. [22] “Experiments to determine the Force of fired Gunpowder.” Phil. Trans. vol. lxxxvii. p. 254. et seq. [23] See a very ingenious application of this kind in Mr. Babbage’s article on Diving in the Encyc. Metrop.--Others will readily suggest themselves. For instance, the ballast in reserve of a balloon might consist of materials capable of evolving great quantities of hydrogen gas in proportion to their weight, should such be found. [24] The sulphuric. Bracconot, Annales de Chimie, vol. xii. p. 184. [25] D’Arcet, Annales de l’Industrie, Fevrier, 1829. [26] See Dr. Prout’s account of the experiments of professor Autenrieth of Tubingen. Phil. Trans. 1827, p. 381. This discovery, which renders famine next to _impossible_, deserves a higher degree of celebrity than it has obtained. [27] Greenwich. [28] Maskelyne’s. [29] Thomson’s First Principles of Chemistry, vol. ii. p. 68. [30] Galileo exposes unsparingly the Aristotelian style of reasoning. The reader may take the following from him as a specimen of its quality. The object is to prove the immutability and incorruptibility of the heavens; and thus it is done:-- I. Mutation is either generation or corruption. II. Generation and corruption only happen between contraries. III. The motions of contraries are contrary. IV. The celestial motions are circular. V. Circular motions have no contraries. α. Because there can be but three simple motions. 1. To a centre. 2. Round a centre. 3. From a centre. β. Of three things, one only can be contrary to one. γ. But a motion to a centre is manifestly the contrary to a motion from a centre. δ. Therefore a motion _round_ a centre (_i. e._ a circular motion) remains without a contrary.