Tancred Robinson chosen in the room of Mr. Musgrave. Every body seemed satisfied, and no discontent appeared anywhere, when, on a sudden, Mr. Aston, as I suppose, willing to gain better terms of reward from the Society than formerly, on December 9th, in Council, declared that he would not serve them as Secretary; and therefore desired them to provide some other to supply that office; and that after such a passionate manner, that I fear he has lost several of his friends by it. The Council, resolved not to be so served for the future, thought it expedient to have only honorary secretaries, and a clerk or amanuensis, upon whom the whole burthen of the business should lie, and to give him a fixed salary, so as to make it worth his while, and he to be accountable to the secretaries for the performance of his office; and, on January 27th last, they chose me for their under officer, with a promise of a salary of fifty pounds per annum at least."

Notwithstanding Mr. Aston's conduct, the Council ordered that he be presented with a gratuity of £60. About two months and a half after Mr. Aston's demission, Newton addressed to him a letter, dated February 23, 1684-5, in which he states, that the attempt made by himself and Mr. Charles Montague to establish a Philosophical Society at Cambridge, had failed.

Mr. Aston does not seem to have taken offence at these proceedings of the Council. He communicated to the Society some observations on certain unknown ancient characters, which were published in the Philosophical Transactions for 1692; and, previous to his death, which seems to have taken place in 1715, he bequeathed to the Royal Society a small estate, still possessed by them, at Mablesthorpe, in Lincolnshire, consisting of 55 acres, 2 roods, and 2 perches. He likewise left to the Society a considerable number of books and some personal property, which, after paying off certain debts, amounted to £445.1

1

The following letter was written when Newton was only twenty-six years of age. We have not been able to find any account of the information which Mr. Aston communicated to his friend, either during his travels or after his return :—

1 Weld's History of the Royal Society, vol. i. p. 428.

"TRINITY COLLEGE, CAMBRIDGE, May 18, 1669. SIR, Since in your letter you give mee so much liberty of spending my judgement about what may be to your advantage in travelling, I shall do it more freely than perhaps otherwise would have been decent. First, then, I will lay down some general rules, most of which, I believe, you have considered already; but if any of them be new to you, they may excuse the rest; if none at all, yet is my punishment more in writing than your's in reading.

"When you come into any fresh company, 1. Observe their humours. 2. Suit your own carriage thereto, by which insinuation you will make their converse more free and open. 3. Let your discours be more in querys and doubtings than peremptory assertions or disputings, it being the designe of travellers to learne, not to teach. Besides, it will persuade your acquaintance that you have the greater esteem of them, and soe make them more ready to communicate what they know to you; whereas nothing sooner occasions disrespect and quarrels than peremptorinesse. You will find little or no advantage in seeming wiser, or much more ignorant than your company. 4. Seldom discommend any thing though never so bad, or doe it but moderately, lest you bee unexpectedly forced to an unhansom retraction. It is safer to commend any thing more than it deserves, than to discommend a thing soe much as it deserves; for commendations meet not soe often with oppositions, or, at least, are not usually soe ill resented by men that think otherwise, as discommendations; and you will insinuate into men's favour by nothing sooner than seeming to approve and commend what they like; but beware of doing it by a comparison. 5. If you bee affronted, it is better, in a forraine country, to pass it by in silence, and with a jest, though with some dishonour, than to endeavour revenge; for, in the first case, your credit's ne'er the worse when you return into England, or come into other company that have not heard of the quarrell. But, in the second case, you may beare the marks of the quarrell while you live, if you outlive it at all. But, if you find yourself unavoidably engaged, 'tis best, I think, if you can command your passion and language, to keep them pretty eavenly at some certain

moderate pitch, not much hightning them to exasperate your adversary, or provoke his friends, nor letting them grow over much dejected to make him insult. In a word, if you can keep reason above passion, that and watch fullnesse will be your best defendants. To which purpose you may consider, that, though such excuses as this,-He provok't mee so much I could not forbear,―may pass among friends, yet amongst strangers they are insignificant, and only argue a traveller's weaknesse.

"To these I may add some general heads for inquirys or observations, such as at present I can think on. As, 1. To observe the policys, wealth, and state affairs of nations, so far as a solitary traveller may conveniently doe. 2. Their impositions upon all sorts of people, trades, or commoditys, that are remarkable. 3. Their laws and customs, how far they differ from ours. 4. Their trades and arts, wherein they excell or come short of us in England. 5. Such fortifications as you shall meet with, their fashion, strength, and advantages for defence, and other such military affairs as are considerable. 6. The power and respect belonging to their degrees of nobility or magistracy. 7. It will not be time mispent to make a catalogue of the names and excellencys of those men that are most wise, learned, or esteemed in any nation. 8. Observe the mechanisme and manner of guiding ships. 9. Observe the products of nature in several places, especially in mines, with the circumstances of mining and of extracting metals or minerals out of their oare, and of refining them; and if you meet with any transmutations out of their own species into another, (as out of iron into copper, out of any metall into quicksilver, out of one salt into another, or into an insipid body, &c.,) those, above all, will be worth your noting, being the most luciferous, and many times lucriferous experiments too in philosophy. 10. The prices of diet and other things. 11. And the staple commoditys of places.

"These generals, (such as at present I could think of,) if they will serve for nothing else, yet they may assist you in drawing up a modell to regulate your travels by.

"As for particulars, these that follow are all that I can now think of, viz., Whether at Schemnitium, in Hungary, (where there are mines of gold, copper, iron, vitriol, antimony, &c.,)

they change iron into copper by dissolving it in a vitriolate water, which they find in cavitys of rocks in the mines, and then melting the slimy solution in a strong fire, which in the cooling proves copper. The like is said to be done in other places, which I cannot now remember; perhaps, too, it may be done in Italy. For about twenty or thirty years agone there was a certain vitrioll came from thence, (called Roman vitrioll,) but of a nobler virtue than that which is now called by that name; which vitrioll is not now to be gotten, because, perhaps, they make a greater gain by some such trick as turning iron into copper with it, than by selling it. 2. Whether, in Hungary, Sclavonia, Bohemia, near the town Eila, or at the mountains of Bohemia near Silesia, there be rivers whose waters are impregnated with gold; perhaps, the gold being dissolved by some corrosive waters like aqua regis, and the solution carried along with the streame, that runs through the mines. And whether the practise of laying mercury in the rivers, till it be tinged with gold, and then straining the mercury through leather, that the gold may stay behind, be a secret yet, or openly practised. 3. There is newly contrived, in Holland, a mill to grind glasses plane withall, and I think polishing them too; perhaps it will be worth the while to see it. 4. There is in Holland one Borry, who some years since was imprisoned by the Pope, to have extorted from him secrets (as I am told) of great worth, both as to medicine and profit, but he escaped into Holland, where they have granted him a guard. I think he usually goes cloathed in green. Pray inquire what you can of him, and whether his ingenuity be any profit to the Dutch. You may inform yourself whether the Dutch have any tricks to keep their ships from being all worm-eaten in their voyages to the Indies. Whether pendulum clocks do any service in finding out the longitude, &c.

"I am very weary, and shall not stay to part with a long compliment, only I wish you a good journey, and God be with Is. NEWTON.

you.

Pray let us hear from you in your travells. I have given your two books to Dr. Arrowsmith."

No. II.

(Referred to in page 134.)

As Newton's Hypothesis "touching his Theory of Light and Colours," which he communicated to the Royal Society on the 9th December 1675, and which he afterwards illustrated and extended in his celebrated letter to Robert Boyle in 1679, is very little known, and must ever be referred to in the History of Optical Discovery, we have reprinted these two interesting documents:

AN HYPOTHESIS1 EXPLAINING THE PROPERTIES OF LIGHT DIS

COURSED OF IN MY SEVERAL PAPERS.

"SIR,-In my answer to Mr. Hook, you may remember I had occasion to say something of hypotheses, where I gave a reason why all allowable hypotheses in their genuine constitution should be conformable to my theories, and said of Mr. Hook's hypothesis, that I took the most free and natural application of it to phænomena to be this:-That the agitated parts of bodies, according to their several sizes, figure, and motions, do excite vibrations in the æther of various depths or bignesses, which being promiscuously propagated through that medium to our eyes, effect in us a sensation of light of a white colour; but if by any means those of unequal bignesses be separated from one another, the largest beget a sensation of a red colour, the least or shortest of a deep violet, and the intermediate ones of intermediate colours, much after the manner that bodies, according to their several sizes, shapes, and motions, excite vibrations in the air of various bignesses, which, according to those bignesses, make several tones in sound, &c.' I was glad to understand, as I apprehended from Mr. Hook's discourse at my last being at one of your assemblies, that he had changed his former notion of all colours being compounded of only two original ones, made by the two sides of an oblique pulse, and In a letter to Oldenburg, dated January 25, 1675-76.

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