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Torpedo. - Magnetic Needle. Nairne's Electricai Machine. — Magazines at Purfleet.

London, 30 September, 1773. MY DEAR FRIEND, I rejoiced as much as any friend could do at the news we received here from time to time of your success in your profession, and of the safe recovery of your illustrious patients of that most amiable family. But it grieved us all, at the same time, to hear that you did not yourself enjoy health in that country. Surely their known goodness will graciously give you leave of absence, if you have but the courage to request it, and permit you to come and reside in England, which always agreed well with your constitution. All your friends here will be made happy by such an event.*

I had purposed to return to America this last summer, but some events in our Colony affairs induced me to stay here another winter. Some time in May or June next I believe I shall leave England. May I hope to see you here once more ?

I shall be glad to see the work of the Abbé Fontana on that disease of wheat. As yet I have not heard that

I it is come to England.

Sir William Hamilton writes from Naples, that after

* Dr. Ingenhousz was now residing at Vienna, whither he had gone to inoculate for the smallpox the Archduchess Theresa Elizabeth, the only daughter of the Emperor, and the Archdukes Ferdinand and Maximilian, the Emperor's brothers. He remained in that city several years. He was in England during a large part of the year 1779, when he published his work, entitled Erperiments on Vegetables, 8c. In the title-page of that work, he styles himself, “ Counsellor of the Court and Body Physician to their Imperial Majesties." - EDITOR.


many experiments he has not been able to perceive any certain signs of electricity in the torpedo. It is perhaps best that there should be two opinions on this subject, for that may occasion a more thorough examination of it, and finally make us better acquainted with it.

It is not difficult to construct a needle, so as to keep pointing to the meridian of any one place, whatever may be the variation in that place. But to point always to the meridian, wherever the needle may be removed, is, I apprehend, not possible.

Mr. Nairne has, as you have heard, finished a very fine electric machine. I have seen sparks from the prime conductor thirteen inches in length. He has added a large battery, and produces a discharge from it sufficiently strong to blast growing vegetables, as lightning is supposed to do. From a greater force used, perhaps some more discoveries may be made. I am much pleased with the account you give me of your new machine of white velvet rubbed upon hareskin.

Last year the Board of Ordnance applied to the Royal Society here for their opinion of the propriety of erecting conductors to secure the powder magazines at Purfleet. The Society appointed a committee to view the magazines, and report their advice. The members appointed were Messrs. Cavendish, Watson, Delaval, Robertson, Wilson, and myself. We accordingly, after viewing them, drew up a Report, recommending conductors to each, elevated ten feet above the roof, and pointed at the ends. Mr. Delaval did not attend; all the rest agreed in the Report, only Mr. Wilson objected to pointing the rods, asserting that blunt ends or knobs would be better. The work, however, was finished according to our direction. He

was displeased, that his opinion was not followed, and has written a pamphlet against points. I have not answered it, being averse to disputes. But in a new translation and edition of my book printed lately at Paris, in two volúmes, quarto, you will see some new experiments of mine, with the reasonings upon them, which satisfied the committee. They are not yet printed in English, but will be in a new edition now printing at Oxford, and perhaps they will be in the next Transactions.*

It has been a fashion to decry Hawkesworth's book; but it does not deserve the treatment it has met with. It acquaints us with new people having new customs, and teaches us a good deal of new knowledge.

Captain Phips has returned, not having been able to approach the Pole nearer than eighty-one degrees, the ice preventing.

M. Tremont, an ingenious young Italian, who was lately here, gave me a little spyglass of his making, upon Père Boscovich's principles, the ocular lens being a composition of different glasses instead of the objective. It is indeed a very good one.

Sir John Pringle is returned from Scotland, better in health than heretofore. He always speaks of you

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* See these experiments in Vol. V. p. 435. A copy of M. Dubourg's French translation of Dr. Franklin's writings, above alluded to, was sent by him to Harvard College. The following complimentary vote of the Corporation was returned.

“ At a meeting of the Corporation of Harvard College, May 31st, 1774.

“Dr. Franklin having presented to our Library a French Translation of his Philosophical Writings in two volumes quarto, a copy which we receive with particular pleasure, as it is a testimony of the sense foreigners have of the merit of these writings, which must do honor to the country that gave him birth, as well as to every literary Society he is related to; Voted, that the thanks of this Board be given to Dr. Franklin for this valuable present, and that Dr. Cooper do transmit him a copy of this vote.

NATHANIEL APPLETON, “ Senior Fellow of the Corporation.” with respect and affection, as does Dr. Huck and all that knew you. I am ever, with the sincerest esteem, dear Sir, Your faithful and most obedient servant,



Experiments on Alkaline Air.

Calne, 14 October, 1773. DEAR SIR, I hope you received my letter, in which I gave you some account of my discovery of an alkaline air, though I have not had the pleasure of hearing from you since. I am still busy in examining its properties and affinities, some of which are curious enough. The most remarkable observation I have made is, of the manner in which it affects alum put into it. This substance absorbs it very fast, and then comes out perfectly white, and altogether unlike what it was; but I have not yet examined it any further.

I have also found, that this alkaline air is slightly inflammable. This is not observed without attention, for a candle dipped into it goes out several times before there is much appearance of its inflammability. This, however, agrees with the opinion of chemists, that volatile alkali contains phlogiston.

As you have not written to me, I hope you are planning an excursion to Calne with Sir John Pringle, or some of our friends. This would make me very happy. I am, with great respect, &c.



* Six weeks after the date of the above letter, that is, on the 30th of November, 1773, Dr. Priestley received from the Royal Society the VOL. VI. 52



Communicating a Philosophical Paper.

Lichfield, 24 January, 1774. DEAR SIR, I have enclosed a medico-philosophical paper, which I should take it as a favor if you will communicate to

Copley Medal, in honor of his discoveries of various properties of air. For the Discourse of the President of the Royal Society on the occasion, see Sir John PRINGLE's Six Discourses, p. 1.

Before the Council of the Society had decided on bestowing the medal, Dr. Franklin was requested to examine Dr. Priestley's book and report his opinion. To a nobleman, a member of the Council, (whose name is not written on the draft of the letter that remains,) he replied as follows.

“My Lord; In obedience to your Lordship's cominands, I have looked over that part of Dr. Priestley's work, that contains an account of the experiments made by him. I find there is a great number of them, mostly quite new, and some I think very curious and important, well deserving for that reason, and for the great pains and expense he has been at in making them, the honor of the Society's medal. I am, however, so engaged at present, that I could not possibly prepare any thing of the kind, fit to be laid before the Council on Thursday, and hope your Lordship will be so good as to excuse me., I do not see that his account of them can well be abridged; and, as the book has been long published, and probably is in the hands of all those of the Society, who, from their acquaintance with the subject, are the best judges of the merit of such experiments, I apprehend that any other account is hardly necessary. With the greatest respect," &c. - Editor.

• An acquaintance of long standing, and a correspondence on philosophical subjects, seem to have subsisted between Dr. Franklin and Dr. Darwin, but none of Franklin's letters to Darwin have come within my researches. The only record of their intercourse, contained in Miss Seward's “ Memoirs of Dr. Darwin,” is the following anecdote. “ When he wrote to Dr. Franklin, complimenting him on having united philosophy to modern science, he directed his letter merely thus, ' Dr. Franklin, America,' and said he felt inclined to make a still more flattering superscription; Dr. Franklin, the World. His letter reached the sage who first disarmed the lightning of its fatal power, for the answer to it arrived, and was shown in the Darwinian circles; in which had been questioned the likelihood of Dr. Franklin ever receiving a letter of such general superscription, as the whole western empire," SEWARD's Memoirs of Dr, Darwin, p. 152. - Editor.

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