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gots, or infects, in the husk of one fingle grain, viz. in the first corn fifteen, in the fecond nineteen, in the third twenty-nine, and in the fourth forty-one. So large a number as forty-one infects in one fingle grain, feems fufficient to eat up all the corn in a whole ear: and we muft fuppofe, either that, like the northern nations of old, or modern Arabs, when they have confumed all their old ftock, they decamped in fearch of more; or that they are starved and perish in their citadel. This laft feems the moft likely,-as, first, it appears difficult for them to get out; and, next, fhould fuch innumerable multitudes all furvive, or did not innumerable multitudes perish, they would threaten us with an entire deftruction of the next wheat harvest.

of the yellows, much more fo than thofe which were not elder-ftruck: and I have little doubt but that, had the operation been performed fooner, it would have totally prevented their being at all touched. But the evening before they were ftruck, in going through the fields, and looking attentively at the ears of corn, I difcovered vaft numbers of the flies which occafion the damage, already on the corn, feven or eight flies on a fingle ear. Therefore I have no doubt but that the eggs of the yellows, which are there now, were lodged before the corn was ftruck with the elder; as prevention, and not cure, is all to be expected from the operation. -I took notice of the manner of • the flies. They are about the fize of gnats, with a yellow body, and blueith wings, depofiting their eggs which they do on the outfide of the husk of the ear, about the upper or middle part of the hufk; from whence, I fuppofe, they defcend into the husk by the next fhowers of rain, or dews. One fly in particular I faw lay a great number of eggs, after the rate of about one egg every fecond of time, till at length I caught her by the wing; and, in carrying her acrofs three or four ridges, I thought I perceived fomething on my thumb, which I took up, and, on viewing it through a pocket microfcope, found it to be at least eight or ten eggs, of an oval form, which fhe had laid in that time, and which I preferved for fome time, and fhewed to feveral people.-Judge then of their fecundity. As a further proof of which, I will in form you, that the day I received your letter, I examined fome corns of one ear, and found the follow-.. ing numbers of living yellow mag

I am much obliged to you for the opportunity you have afford. ed me of repeating my respects for your laudable Society, and fubfcribe myself, as with great truth I am,

Your obliged

and obedient fervant, CHRIS. GULLETT.

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My Lords and Gentlemen, THOUGHT it neceffary, at the introducing of the model,

which I hope will be found a preventive against the ill effects of mercury in water-gilding, to endeavour to explain its use, as follows:

The injury received, is at the time the work remains out of the fire, from which arifes a vifible vapour impregnated with the groffeft part of mercury; which for want of proper conveyance, the workman muft inevitably receive each time he breathes. To prevent thofe ill effects, I have contrived a pair of bellows, which immediately draw the effluvia that would otherwife difperfe about him. The tin receiver, in which runs a tube from the bottom of the bellows, is to receive that part of the vapour which the valve of the bellows repels every time it goes down. This is made of tin, but would be found more efficacious if made of common copper, gilt on the infide with leaf-gold, by reafon of the mercury adhering thereto. It is perhaps proper to mention, what otherwife may be thought an inconvenience, namely, the blowing of the bellows, which may be done at any time by. a boy but as it is not fo laborious as the treading of a turner, and many other ways of bufinefs, perfons fo inclined may work them with a ftirrup, without other affiftance, and will find great benefit by the moderate peripiration it will in courfe bring on; to which a farther precaution might be added, that, if the workman chufes, he may put a piece of gold in his mouth and noftrils; but every continued obftruction to breathing in the manner that nature has ordained, muft prove detrimental to the conftitution;

therefore, upon the whole, I dif-
approve of fuch practices. The
glafs, which I have made to take
off and bring on, as occafion re-
quires, will fupply them. I have
still added one of a different make,
on a plan which I think in the
largest fort of work will be found
most effectual; a draught of which
I have annexed to the model, and
will here briefly defcribe. It is a
frame glazed to go all around the
'tin receiver, and come down as
low as the perfon's lap; two holes
with valves, made of leather, re-
ceive the arms, and will not be
found inconvenient in working,
by reason that the fhirt-fleeves are
then always up.-Having thus far
defcribed the principal parts of
this model, fhall leave it to your
better judgment; and if approv-
ed, will give great pleasure and
fatisfaction to,
Gentlemen,

Your most obedient
humble servant,
J. HILLS.

Rofamond's Row, Clerken
well, Dec. 9th, 1773.

EXPLANATION.

To give a diftinct idea of this invention, a more circumftantial defcription must be attempted; and the intended application being therewith likewife fhewn, a better judgment of its utility may be formed. It is generally understood, that the gilder is placed before an open furnace or raised fire-place, putting in and taking out alternately the pieces of metal that are gilding. The memorial points out, that the injury received is during the time the work is out of the fire. The reason of that is obvious; the workman is

then

then brufhing, or laying on more amalgama, holding the piece almoft under his nofe; and as a fmall degree of heat raifes mercury into fumes, it readily occurs, that the heat of the metal forms that noxious vapour which he receives into his lungs every time he breathes, unless it be diverted by fome current of air; and then its baneful effect may in a lefs degree fpread in the room, ftill be felt by him and thofe who are obliged to be with him. To remove all that mifchief, the inventor has thought of collecting the noxious vapour together, and conveying it directly up into the chimney. To do this he has contrived a funnel fixed against the breast of the chimney, over the fpot where the work is held during the operation, and from which the fumes muft rife into it. This funnel, or receiver, as he calls it, is, as to fhape, like a common, wide, fatted, tin tube, with a joint or return in the upper part, carried through the brick work into the fue, as a channel of conveyance into the chimney: but the afcent of the vapour being flow and uncertain, without a draught of air to lead it up, he hath further contrived a tin pipe, one end of which is fixed in the lower part of the funnel, and the other in the valve or draught-hole of a large fized bellows, refting upon the upper part or returning joint of the funnel, and having its nozle led (over the funnel) through the brick-work into the flue. The effect of these bellows is to draw up and force the floating fumes into the chimney; and that is obtained by the operator's working them with his foot, by means

of a line faftened to the upper handle of the bellows, and carried over a pulley fkrewed into the ceiling, or into a piece of wood projecting from the chimney, and thence brought down and tied to a ftirrup, with which it is moved up and down like a treadle.Another part of the invention is a glazed frame or window-fah, placed between the operator and his work, to fkreen him from the approach of the noxious fumes; it is either ftraight, and of the breadth of the chimney, without a return, and made to flide up and down; or elfe, as he fays, for large work made circular, and of a fize to compass the funnel, and close against the corners of the chimney; and then, inftead of a fliding part, to have in front two of the fquares not glazed, but lined with leather fleeves for the arms to pafs through to the work; which by either of thofe modes of prevention, he affures, may be done without hurt to the health of the operator.

The fubicct of the memorial, and the invention difclofed by the model, being taken into confideration, the Society refolved, That a machine of a proper fize for a common chimney fhould be conftructed at their expence; and Mr. Platts, a workman in the watergilding way, being found willing to make the trial, the machine was put up in his room; and a day being fixed, feveral members of the Society went to fee its ef fect, and reported, that they had not felt any of the (fo called)fweet vapour during the operation; after which the following letter was received by the fecretary:

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Sir,

To Mr. More.

HAVING been informed it was neceffary that I fhould deliver my opinion of the machine for preventing the ill effects of mercury in water-gilding, I have the pleafure to inform you, that I have made use of it ever fince the trial, and wish I had been fo happy as to have had the use of fuch an invention twenty years ago: I make no doubt but I fhould have been free from the disorder I have fo long laboured under. As the gentlemen have been fo indulgent as to favour me with the opportunity of experiencing thefe falutary effects, I fhall from gratitude be ready to inform every perfon of the construction of the machine, as far as lies in my power. I am, Sir,

your humble fervant,

M. PLATTS.

Upon the confirmed report, and the additional circumftances of cheapness and fimplicity of conftruction, recommended in the advertifement for the prefervation of the health of poor workmen, it was refolved, That the candidate, Mr. J. Hills, was juftly entitled to the premium, being twenty guineas, offered for difcovering to the Society an effectual method of preventing the ill effects in watergilding filver, copper, or other metals.

N. B. Mr. Hills, originally a feal-engraver, fince moved to No. 82, Berwick-ftreet, Soho, keeps a fhop of natural and artificial curiofities; and of glass ftained by his particular invention,

Account of the Usefulness of Wafhing the Stems of Trees. By Mr. Robert Marsham, Stratton, F. R. S. From the Philofophical Transactions, vol. lxxi. part 2.

THE

HE following account is a kind of poftfcript to my let ter to Dr. Mofs, Lord Bifhop of Bath and Wells, in 1775, which the Royal Society did me the honour to publish in the Philofophical Tranfactions in 1777. In that I fhewed how much a beech increafed, upon its ftem being cleaned and washed; and in this I fhall fhew, that the benefit of cleaning the ftem continues feveral years; for the beech which I washed in 1775 has increased in the five years fince the washing, eight inches and fix-tenths, or above an inch and feven-tenths yearly; and the aggregate of nine unwashed beeches of the fame age does not amount to one inch and threetenths yearly to each tree. In 1776 I washed another beech (of the fame age, viz. feed in 1741); and the increase of four years fince the washing is nine inches and two-tenths, or two inches and three-tenths yearly, when the aggregate of nine unwashed beeches amounted to but one inch and three-tenths and a half. In 1776 I washed an oak which I planted in 1720, which has increased in the four years fince wafhing feven inches and two-tenths; and the aggregate of three oaks planted the fame year (viz. all 1 meafured) amounted to but one inch yearly to each tree. In 1779 I washed another beech of the fame age, and the increase in 1780 was

three

three inches, when the aggregate
of fifteen unwashed beeches was
not full fifteen inches and fix-
tenths, or not one inch and half a
tenth to each tree; yet moft of
of these trees grew on better land
than that which was washed. But
I apprehend the whole of the ex-
traordinary increase in the two last
experiments should not be attri-
buted to washing; for in the au-
tumn of 1778 I had greafy pond-
mud fpread round fome favourite
trees, as far as I fuppofed their
roots extended; and although
fome trees did not fhow to have
received any benefit from the mud,
yet others did; that is, an oak in-
creased half an inch, and a beech
three-tenths above their ordinary
growth. Now though the beech
gained but three-tenths, yet, per-
haps, that may not be enough to
allow for the mud; for the fum-
mer of 1779 was the moft unge-
nial to the growth of trees of any
fince I have measured them; fome
not gaining half their ordinary
growth, and the aggregate increafe
of all the unwashed and unmudded
trees that I measured (ninety-three
in number of various kinds) was
in 1779 but fix feet five inches
and seven-tenths, or seventy-feven
inches and feven-tenths, which
gives but, eight-tenths and about
one-third to each tree; when in
1778 (a very dry fummer in Nor-
folk) they increafed leven feet and.
nine-tenths, or near eighty-five
inches, which gives above nine
tenths to each tree: and this fum-
mer of 1780, being alfo very dry,

*

yet the aggregate increase was ebove half an inch more than in 1778. But the best increase of thefe three years is low, as there are but twenty of the ninety-three trees that were not planted by me, and greater increase is reasonably expected in young than old trees; yet I have an oak, now two hundred years old (1780) which is fixteen feet and five inches in cir. cumference, or one hundred and ninety-feven inches in two hun dred years. But this oak cannot properly be called old. The annual increase of very old trees is hardly, meafurable with a ftring, as the flighteft change of the air will affect the ftring more than a year's growth. The largest trees that I have measured are fo far from me, that I have had no op portunity of meaturing them a fecond time, except the oak near the honourable Mr. Legge's Lodge in Holt Foreft, which does not flew to be hollow. In 1759 I found it was, at feven feet (for a large fwelling rendered it unfair to measure at five or fix feet) a trifle above thirty-four feet in circumference; and in 1778 I found it had not increased above half an inch in nineteen years. This more entire remain of longevity merits fome regard from the lovers of trees, as well as the hollow oak at Cowthorpe in Yorkihire, which Dr. Hunter gives an account of in his edition of Evelyn's Silva, and calls it forty-eight feet round at three feet. I did not measure it fo low; but in 1768 I found it, at

I cannot mistake in the age of this oak, as I have the deed between my anceftor Robert Martham and the copyhold tenants of his manor of Stratton, dated May 20, 1580, upon his then inclofing fome of his wafte; and the abuttal is clear.

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