much struck with the mechanical means he had brought to bear on the subject, and was speculating on other applications of it, which I will presently mention.
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 as 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 inquired 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 inquiring 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
