[82] I here allude to an anecdote related by Mr. Babbage, in his "Reflections on the Decline of Science in England;" a work, by the by, which strongly reminds me of a practical bull. A gentleman, anxious to escape the tax on armorial bearings, wrote a long letter to the Commissioners, stating I do not know how many reasons to show that he could never have used them; and, after all, sealed the letter with his own coat of arms! Had Mr. Babbage hoped to convince the reader that Science was actually on the decline in this country, he should never have written a work which gives the lie to the title-page. Now for the anecdote.--"Meeting Dr. Wollaston one morning in the shop of a bookseller, I proposed this question: If two volumes of hydrogen and one of oxygen are mixed together in a vessel, and if by mechanical pressure they can be so condensed as to become of the same specific gravity of water, will the gases, under these circumstances, unite and form water? 'What do you think they will do?' said Dr. W. I replied, that I should rather expect they would unite. 'I see no reason to suppose it,' said he. I then enquired whether he thought the experiment worth making. He answered, that he did not, for that he should think it would certainly _not_ succeed. "A few days after, I proposed the same question to Sir Humphry Davy. He at once said, 'They will become water of course:' and on my enquiring whether he thought the experiment worth making, he observed that it was a good experiment, but one which it was hardly necessary to make, as it must succeed. "These were off-hand answers, which it might perhaps be hardly fair to have recorded, had they been of persons of less eminent talent; and it adds to the curiosity of the circumstance to mention, that I believe Dr. Wollaston's reason for supposing no union would take place, arose from the nature of the electrical relations of the two gases remaining unchanged: an objection which did not weigh with the philosopher whose discoveries had given birth to it." Davy succeeded in liquefying gases by a method which, at first view, appears very paradoxical--_by the application of heat!_ The method consists in placing them in one leg of a bent sealed tube, confined by mercury, and applying heat to ether, or alcohol, or water, in the other end. In this manner, by the pressure of the vapour of ether, he liquefied prussic gas and sulphurous acid gas; which gases, on being reproduced, occasioned cold.