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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 disco very ;-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. “ 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 disco verer ? 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.”

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.f Lord Brongham says that Blagden's legacy was generally understood to have fallen far short of his ample expectations. I

* By Lord Brougham, of Lavoisier, ary, 1804, and commences with the in the Life of Dr. Black.—Lives of bequest to Sir C. Blagden. It was “Men of Letters and Science,' vol. i., proved 5th March, 1810.

| Lives of Men of Letters and + Mr. Cavendish's latter will we Science,' vol. i. p. 446. have seen. It was made 18th Febru

p. 329.

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 5001. 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 18,5001. on account of the annuity, making, together with the legacy of 15,0001., a round sum of 33,5001., 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.

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 con. duct 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 those circumstances Blagden gave an account which he professed to be “the “ best,” of “the little dispute about the first discoverer of the " artificial generation of water,” and therein asserted the priority of both Cavendish and Watt over Lavoisier, but scarcely ventured to hint, even in the most vague and general way, at any priority of Cavendish over Watt, it is very certain that, wbatever 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.

* See Wilson's Life of Cavendish.'

CHAPTER XXII.

ARGUMENTS OF THE ADVOCATES OF CAVENDISH - THEIR GROUNDLESSNESS

- PRIORITY OF WATT MAINTAINED DURING HIS LIFETIME OPINIONS OF PHILOSOPHERS SINCE HIS DEATH DR. HENRY SIR HUMPHRY DAVY - LORD BROUGHAM ARAGO DUMAS BERZELIUS SIR DAVID BREWSTER LORD JEFFREY — LIEBIG — MR. WATT'S SCRUPULOUS SENSE OF JUSTICE -HIS ACQUAINTANCE WITH CAVENDISH -FESTIVITIES OF 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.,

of Mr. Watt's paper “on the Constituent Parts of Water, ” in describing Dr. Priestley's experiment, it is said,—" The “ moisture adhering to the glass after these deflagrations, “ being wiped off, or sucked up by a small piece of sponge

paper, first carefully weighed, was found to be exactly, or very nearly, equal in weight to the airs employed.And,— “ These two kinds of air unite with violence, they become “ red-hot, and, upon cooling, totally disappear. When the “ vessel is cooled, a quantity of water is found in it equal to the weight of the air employed.". So in Mr. Watt's Correspondence," he finds on the side of the vessel a quantity of water equal in weight to the air employed.” † And again, “ No residuum, except a small quantity of water equal to their weight." ! So also, “ you will find the water, (equal in weight to the air), adhering to the sides of the vessel.” § The circumstance of the equality of weight was indeed one of the facts on which Mr. Watt repeatedly states that he founded his deductions; and, as will presently be seen, it is of great importance in more points of view than one.

The substitution of the term hydrogen for phlogiston, had been so amply explained by M. Arago, in the note on that subject which accompanied Lord Brougham's Historical Note,|| that it might have been supposed no fair objection could have been raised to it by any one; even by the most injudicious and ill-informed partisan of Mr. Cavendish. M. Arago was also at the pains to produce a letter from Dr. Priestley to M. Lavoisier, dated 10th July, 1782, in which he says he has made “some experiments with inflammable air, that seem to

prove that it is the same thing that has been called phlogiston.Dr. Priestley, in relating, in his paper of 1785, the theory which Mr. Watt had formed, says that he “concluded, &c., “ that water consists of dephlogisticated and inflammable air.But further, the professed difficulty might have been removed, if those who made it had chosen to profit by Mr. Watt's own

s Phil. Trans.,' 1784, pp. 332, 333.

† Mr. Watt to Mr. Gilbert Hamilton, 26 March, 1783.

I The same to the same, 22 April,

1783.

$ Mr. Watt to Mr. Fry, 28 April, 1783.

Il • Eloge of Watt,' p. 167.

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