wonder, so strong their disbelief. But Mr. Cavendish's friends are not said by Blagden to have testified any surprise, or any incredulity; yet "the conclusions," as Lord Brougham has truly said, "are identical," with the single difference as to heat, in which respect the discoveries of modern chemists have shown that Mr. Watt's had greatly the advantage. But the novelty was gone, and the disbelieving wonder had ceased. When Blagden says only, that both communications were made in "the Spring," and "about the same time,” he claims for his patron no priority; he is content to insinuate for him only a very questionable sort of independence in the discovery;-nay more,-for that is the result to which the evidence brings it, he can for Mr. Cavendish, as against Mr. Watt, neither claim priority, nor establish independence.

In Mr. Cavendish's paper as first written, and as read on the 15th January, 1784, he made no mention whatever of Mr. Watt's theory. Yet it appears from the letter to Crell, that Blagden was not uninformed at a much earlier period, (viz. the Spring of 1783), of Mr. Watt having formed "an opinion" similar to that of Cavendish; he confesses that "the news "was brought to London" in the same Spring; that he knew it, at latest, before June; and he authorised Kirwan to tell Mr. Watt that he had even heard his paper read; the 'Philo'sophical Transactions' prove that it was known, from Mr. Watt's own letter, to many members of the Royal Society; De Luc says it was known to all the active members, and to Dr. Blagden especially, who had full acquaintance with Mr. Cavendish's paper, both before it was read, and at its reading; and, lastly, it is highly probable that Blagden first heard of Mr. Watt's theory from Cavendish himself,—at least Mr. Watt evidently so interpreted Kirwan's letter. Blagden certainly nowhere asserts that Cavendish was not aware of it. Neither does Cavendish himself. Why, then, did he suppress, so far as depended on him, all notice of the theory which had thus been formed elsewhere, and of which he well

knew the vast importance,-which was then many months old,—and to which his own was so wonderfully conformed as to be justly termed, "its proof and exposition, word for word?" Why did he so readily grasp at the undivided merit of the discovery, but never once name the discoverer who had been treading, as even he must have admitted, with no unequal steps, and, as it was very soon proved, even in advance of himself, in the same path?

But, in the next place, when,-after Mr. Watt's paper had been read to the Royal Society,—Blagden added a passage, which was adopted and printed as his own by Cavendish, and therein mentioned both the name and the theory of Mr. Watt, why did neither of the two coadjutors say a single word to enlighten the scientific world on the dates at which the two theories respectively were formed? Or, was this unaccountable and highly suspicious desideratum supplied, when, at a later period, Blagden undertook to give his "best account of the matter? On the contrary, although he declares Lavoisier to have known of the conclusions of both Watt and Cavendish, and, therefore, to have been posterior to both, he is still satisfied with trying loosely to couple those two together, as having arrived at the discovery somewhere “about "the same time." "Those conclusions," says Blagden, "opened the way to M. Lavoisier's present theory;" and he thus informs us who was, of three, the last discoverer. Why does he not, in "the best account" of "the little dispute," venture to state the knowledge, which we well know he must have possessed, as to which of the other two was the first discoverer? That was the only point which he professed to settle; that is the only one which he leaves altogether untouched. His "best account" is indeed a miserably bad one, alike for himself and his friend; and of his phrase "about the same "time," it has been happily observed,* in the case of another philosopher, that it was used "with a convenient degree of ambiguity, just sufficient for self-defence, should he be charged with unfair appropriation."

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By Lord Brougham, of Lavoisier, in the Life of Dr. Black.-Lives of

Men of Letters and Science,' vol. i., p. 329.

Such is the whole state of the case for Cavendish; utterly deficient in any real claim to priority, even on the statement of his own friends,-let us rather say, of the only friend who has attempted to give testimony, solitary, partial, and obscure, in his favour.

There is one other point, on which, however, we touch unwillingly and briefly, because it is of a delicate nature, and we have no desire, nor, indeed, occasion, to draw from it any conclusion. For, as has been fully shown, Dr. Blagden's statements, even if perfectly correct, cannot be said to contradict Mr. Watt's priority. But it certainly ought not to be kept altogether out of sight, in estimating the value of any testimony given by Dr. Blagden on behalf of Mr. Cavendish, that he received from that distinguished chemist, both a considerable annuity for a great part of his life, and afterwards a legacy of fifteen thousand pounds. Lord Brougham says that Blagden's legacy was generally understood to have fallen far short of his ample expectations.†

*

With regard to the annuity, the following appear to be the facts, as far as they can now be ascertained. Early in 1783, Blagden became Cavendish's assistant; an annuity of 5007. being settled on him as his recompense for undertaking that office. In 1789, Cavendish and his assistant are said to have parted; causa latet. But the expression, that the annuity "was settled" on Blagden, leads us to suppose, in the absence of any information to the contrary, that it continued to be paid to him till the time of his death, which took place in 1820. Thus a sum of 18,500l. on account of the annuity, making, together with the legacy of 15,000l., a round sum of 33,5007., was received by Blagden from Cavendish for six years' service as his assistant. The money so got, increased and multiplied, it is said, by speculations in the French funds;and he, who began life as a poor army-surgeon, died a wealthy man, the probate of his will being sworn under 50,0007.

*Mr. Cavendish's latter will we have seen. It was made 18th February, 1804, and commences with the bequest to Sir C. Blagden. It was

proved 5th March, 1810.

Lives of Men of Letters and 'Science,' vol. i. p. 446.

See Wilson's Life of Cavendish.'

We are far from wishing to press the idea, that there was any deliberate intention on the part of Cavendish to exercise an undue influence over Blagden, by making him so large a recipient of his bounty in return for services rendered for so brief a time; or any design on the part of Blagden to earn his wages by the commission of iniquity; especially as the persons concerned in the matter no longer survive to defend themselves, and explain those parts of their conduct which may appear singular or doubtful. But in estimating the value, as evidence, of Blagden's testimony on behalf of Cavendish, we must unquestionably take into account the relative position of the parties, and the unavoidable bias by which such testimony must have been affected. Without doing or intending wrong to any one, or to any one's memory, we may venture to assert with perfect confidence, that when under these circumstances Blagden gives an account which he professes to be "the "best," of "the little dispute about the first discoverer of the "artificial generation of water," and therein asserts the priority of both Cavendish and Watt over Lavoisier, but scarcely ventures to hint, even in the most vague and general way, at any priority of Cavendish over Watt, it is very certain that, whatever might be the value of his evidence on the first of those points, it must be held to be conclusive against Cavendish on the second of them.

PRIORITY OF WATT MAINTAINED DURING HIS LIFETIME OPINIONS OF PHILOSOPHERS SINCE HIS DEATH DR. HENRY - SIR HUMPHRY DAVY DUMAS BERZELIUS - SIR DAVID

LORD BROUGHAM

ARAGO

BREWSTER - LORD JEFFREY LIEBIG MR. WATT'S SCRUPULOUS SENSE

OF JUSTICE HIS ACQUAINTANCE WITH CAVENDISH
THE ROYAL SOCIETY.

BESIDES employing the argument arising from the reputation of Mr. Cavendish, which does not really affect the question of priority in the discovery, if established by other evidence, the advocates of Cavendish have made three principal assertions with the view of impugning M. Arago's accuracy. They have said, first, that Priestley "constantly maintained" that he had never found the weight of the water, produced in his experiment, equal to that of the gases exploded; secondly, that an undue licence had been used, in substituting the term hydrogen for phlogiston, as used by Mr. Watt; and thirdly, that the conclusions of Cavendish, which were first stated to the Royal Society in his paper read on the 15th of January, 1784, must be supposed to have been included, or involved, in his experiments made in 1781.

The first of these assertions might well be termed by M. Arago "inconceivable," when it is remembered that in Priestley's own paper he says,-" In order to judge more accurately "of the quantity of water so deposited, and to compare it "with the weight of the air decomposed, I carefully weighed "a piece of filtering paper, and then having wiped with it "all the inside of the glass vessel in which the air had been decomposed, weighed it again; and I always found, as near "as I could judge, the weight of the decomposed air in the "moisture acquired by the paper."* In the very first pages

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*Phil. Trans.,' 1783, p. 427.