612

Epitome of the Philofophical Tranfactions.

each end of it, horizontally, and at
right angles, having the points in con-
trary directions. This wooden needle
was then placed, like the needle of a
compafs, on a pin about fix inches
long, which was fixed in the center of
an electric stand, and the stand being
electrifed, the wooden needle turned A
round, carrying the pins with their
heads foremost. The ftand was then
electrifed negatively, upon a fuppofi-
tion that it would turn the contrary
way, but it continued to revolve in the
fame direction.

To account for this, it is fuppofed, that when the ftand was electriled po fitively, the natural quantity of electricity in the air being increased on one fide by what iffued from the points, the needle was attracted by the lefs quantity on the other; and that when the ftand was electrifed negatively, the natural quantity of electricity in the air was diminished near the points, and the equilibrium being destroyed, the needle was attracted by the greater quantity on the other.

Upon this principle the doctrine of repulfion in electrifed bodies becomes doubtful, for all phænomena that have been fuppofed to indicate it may be accounted for without it.

B

Cork balls feparate when ele&trifed negatively, as far as when electrifed-P pofitively, and in both cafes the feparation may be accounted for by the mutual attraction of the natural quantity in the air, and that which is den. fer or rarer in the cork-balls; for quantities of the electric fluid in different denfities, mutually attract each other till the equilibrium is restored.

That the air has its common ftock E of electricity as well as all electrics per fe, may be demonstrated by the following experiment:

EXP. V. Let a perfon in a negative ftate, out of doors in the dark, when the air is dry, hold a long tharp needle, pointing upwards, extending his arm as high as he can, the electricity colJected from the air will foon appear luminous as it converges to the point F of the needle.

EXP. VI. To determine whether the air, in clear dry weather, be of the fame denfity, at the height of 2 or 300 yards, as near the ground, the following experiment was made with the electrical kite.

The twine throughout had a small wire in it. the ends of which, where the feveral lengths united, were tie down to prevent their acting as point

G

the kite itself had three points of me. tal fixed to it, one on the top, the other on each fide, and two cork balls were fufpended on the twine by fine flaxen threads, just above the place where the filk was tied to it, and sheltered from the wind.

The twine appeared to be electrified in a (mall degree by the feparation of the balls, and to be electrified pofitively by applying it to the wire of a charged bottle, which made the feparation of the balls greater, without firft coming nearer together.

EXP. VII. By an experiment with an electrical air thermometer, which cannot be defcribed without a cut, it appeared that the electric fire, when in a state of reft, has no more heat than the matter in which it refides.

EXP. VIII. By this experiment, with the fame thermometer, it appears that the wires when in contact are not heated in the leaft degree by the fire's paffing through them.

EXP. IX. X. Prove that the charge of a three pint bottle, in motion froin one wire to another, produces heat in itfelf, and in the air through which it paffes. The charge of a large jar paffing through fome wet writing paper, a wet flaxen and woolen thread, a blade of green glafs, a filament of green wood, a very small brafs wire, and a trip of gilt paper, produced heat enough to rarefy the air perceptibly. The charge of a cafe of bottles, containing above 30 fquare feet of coated glafs, fent through the brafs wire, confumed great part of it into fmoke. A large quantity will pafs through a large wire without producing fenfible beat, but the fame quantity paffing through a fmall one will make it red hot, and even melt it.

EXP. XI. The charge of the cafe of bottles, paffing through a wire about two feet long, with a pound weight at the end of it, rendered it red hot through its whole length, and the weight at the end, while it was foft, drew it out, fo as to make it an inch longer than before.

EXP. XII. Proved that the wire was not only red, but hot, by enclosing the wire in a goofe quill filled with gunpowder, which took fire as readily as if it had been touched with a hot poker.

It is inferred that lightening does not melt metal by a cold fufion, as has been imagined; but the firing gunpowder does not fimply prove heat, for the electric stream, or fparks, that

fire fpirits of wine warmed into fume,
if received upon the hand, feel cold
and if lightening does not melt metal
by a cold fufion, it is impoffible to
account for the blade of a fword's be-
ing compleatly melted in a fcabbard,
and the fcabbard not finged, and mo-
ney of various metals being melted in-
to one mafs in a pocket, and the pock-
et not changed, even in colour; for
however fuddenly the metal may be
heated by electricity, or lightening,
it would be as long cooling, and pro-
duce the fame effects while it was hot, B
as if heated in a furnace.

XXIII. Obfervations in electricity
and on a thunder storm, by Mr Tor-
bern Bergman, member of the Royal
Academy of Upfal.

That in my bofom revived in about a quarter of an hour; feeling it move, I took it out to look at it, and faw it ftretch itself on my hand, but perceiving it not fufficiently come to itself, I put it. Ain again: In about another quarter, feeling it flutter pretty briskly, I took it out and admired it. Being now perfectly recovered, before I was aware it took its flight, the covering of the boat prevented me from feeing where it went: the bird on the board, though expofed to a full fun, yet, I prefume from a chilliefs in the air, did not revive to be able to fly.

The obfervations in electricity re-
late chiefly to the property in Iceland
chryftal of lofing its electricity by a
moderate heat, obferved by Mr Dela-
pal, and fhew that this property is not
common to all kinds of chryftal, as Mr
Delaval had before obferved.-The
account of the thunder storm relates
particularly to its effects on various
fubftances it met in its way, fimilar to D
others that have been often described.

XXIV. Remarks on fwallows on the
Rhine; in a letter from Mr Acbard in
Privy Garden, to Peter Collinfon, F. R. S.

In the latter end of March, fays
Mr Achard, I took my passage down
the Rhine to Rotterdam; a little below
Bafil the fouth bank of the river was
very high and fteep, of a sandy foil, 60
or 80 feet above the water.

I was furprized at feeing near the top of the clift fome boys tied with Ippes hanging down doing fomething: The fingularity of thefe adventrous boys, and the bufinefs they fo daringly attempted, made us ftop our navigation to enquire into the meaning of it. The watermen told us they were fearching the holes in the clift for fwallows, or martins, which took refuge in them, and lodged there all the winter, until warm weather, and then they came abroad again.

The boys, being let down by their comrades to the holes, put a long rammer with a fcrew at the end, as is ufed to unload guns, and, twisting it about, drew out the birds. For a trifle I procured fome of them. When I first had them, they feemed ftiff and lifeless. I put one in my bofom, between my fkin and fhirt, and laid another on a board, the fun fhining full and warm upon it. One or two of my Companions did the like.

E

Upon this letter, Mr Collinfon remarks, that the taking thefe fwallows was a frequent praclife, and that it confirmed his conjecture, that when fome of the swallow tribe go away, some stay behind in thefe dormitories all the

winter.

XXV. The properties of the mechanical powers demonftrated, by Hugh Hamilton, D. D. This article is not an object of popular attention, and indeed cannot be abridged.

XXVI. An account of fubterranean. apartments with Etrufcan inscriptions. and paintings difcovered at Civia. Turchino in Italy, by Jofeph Wilcocks Elą; . (See this article at large p. 476)

XXVII. An account a new Peruvian plant lately introduced into the English gardens, the characters of which, differ from all the Genera hitherto defcribed; by George Dionyfius Ebret.

This plant flourished in the phyfic garden at Chelsea in 1761, it was prefented by Dr Albert Schloffer of Am-. ferdam to Mr George Dionyfius Ehret, F among other fpecimens which he had. gathered in the botanic garden at Paris under the name of Belladona Peruviana minor. The flowers are monopetalous, or tube fhap'd, having five obtule lacinia, which expand themfelves like thole of the Alkekengi Indicum glabrum chenopodi folio Dill. Hort. Eltb. except that the filaments of the Alkekengi adhere to the bale of the tube, but thofe of this flower are inferted in faux corolla at the swelling of the tube: The colour of the flowers is a fky blue with a dark embroidered purple bottom: The branches fpread on the furface of the ground in great numbers, and fend out lateral ones which grow alternately, each joint is furnished with ovate thaped leaves, having membranous ciliated footftalks. The moft remarkable character of this plant is the pofition of the five fimilar feeds, each of which

H

ha

514

Epitome of the Philofophical Tranfactions."

has its peculiar receptaculum, and
which lay in fuch a manner in the cen-
ter of the calyx, that at first fight it
appeared as if it belonged to the clafs
of plants called herbe verticillate, but
on nearer inspection it appeared that A
each of thefe fimilar feeds was a fepe-
rate feed veffel (or a trifpermous
fruit) and contained three feeds.

XXVIII. Obfervations on two Ro-
man infcriptions discovered at Netherby
in Cumberland, by the Rev. J. Taylor
L. L. D.

For thefe infcriptions the reader is referred to a plate called Tab. XI where they are said to be marked No.

B

and No. 2, but in Tab. XI no infcriptions are to be found, nor is the defect fupplied in the article fo numbered, which mentions also another faid to be marked No. 3, but this is C also wanting. We are told, that No. 1 ferved as a cover to a drain; and that No. z was found in an apartment be.' longing to a large building; they both mention Marcus Aurelius Salvius tribune of the cohors Prima Ælia Hispanorum Millaria Equitata; and one of them points out the particular Emperor M. Aure- D lius Severus Alexander, in whose reign it was engraved : The last words are fuppofed to be these

Y

IMPERATORE DOMINO NOSTRO

SEVERO ALEXANDRO, P10 FELICE, AUGUSTO, CONSULE. And it is obferved that the appella- E tion, Dominus Nofter was given him, notwithstanding what is recorded of him by his hiftorian Lampridius, Dominum fe appellari vetuit, and that, whatever inclination he might have to-wards christianity, his forces in Britain were not in the fecret, as appears by a Pagan compliment which is faid to occur in the fourth line of the infcription in question.

DEVOTANUMINI MAIESTATIQUE EIUS.

The infcriptions which are principally the fubject of this article not being before the public, as doubtless they ought to have been, all that is faid about them is confufed, and unfatisfactory; they are indeed well worth notice as the Roman affairs in Britain are little known under this Emperor, only one infcription bedes bearing his name, or referring to his age, and as

one

of thefe infcriptions is faid to mention Valerianus, a legate, or lieutenant, and propretor in this province, never taken notice of before. A copper infcription lately difcovered in the estate of the Duke of Norfolk in Yorkshire, and now in his Grace's pofeffion, is faid to afford another, nd

that a very remarkable perfonage, un-
der the Emperor Hadrian, and one
much known in the Roman hiftory.
What reafon the author of this article
had not to name him can as little be

gueffed, as why he omitted to exhibit
the infcriptions he thought fit to write
a differtation upon and refer to.

XXIX. A method of leffening the
quantity of friction in engines by
Keane Fitsgerrald, Efq; The method
here propofed is the fame with what
has been long known and practifed un-
der the name of friction wheels, a con-
trivance by which the pivets of one
wheel turn on the periphery of others;
the ingenious Mr Ellicot demonftrated,
what could be effected by this contri-
vance more than 20 years ago, in a
weights, which he conftructed for that
fmall machine put in motion by
purpofe, only the author of this article
fubftitutes a fecond fet of friction
wheels, on the peripheries of which
the pivets of the first fet turn, as the
pivet of the original wheel turns on
the periphery of the firit fet of friction
from friction may be reduced to le's
wheels, by which, he says, the resistance
than the refiftance of the medium
through which the wheel paffes. A-
nother advantage is alfo faid to arife
from these wheels, that if the motion'
is required to be swift, though the pi-
raifed will allow, yet they scarcely
vets be as fmall as the weight to be
ever wear the holes in which they turn,
for the last pivots in a treble fet of
wheels, which are the only ones that
rub on a dead furface, will hardly
make one revolution in two days.

This article contains fome useful obfervations on the engine for raising water by fire; and fhews that confiderable advantage is gained by placFing the axis above the lever, instead of below it; it alfo fhews, how the friction may be leffened, upon the principle of friction wheels by quadrants, but thefe particulars cannot be comprehended without the cut, by which the author has illuftrated them. between the obfervatories of London XXIX. The difference of longitude and Paris, determined by obfervations of the tranfit of Mercury over the fun in the years 1723, 1736, 1743, and 1753, by James Short.

G

H

The difference of longitude between aftronomers been thought to be 9m. thefe two places has by the Engli 20f. and by the French, gm. 1of. bus in this article, the difference calculated from 63 obfervations of the con

ta&

tact of Mercury with the fun's limb
made at each place, appear to be 9m.16f.
ART. XXX (See next page)'
(To be continued.)

Mr URBAN,

IN

would certainly have been very unwilling to go through fuch a long, dry, and tedious detail of the variety of the parts. I was but too apprehenfive of having faid too much, even upon the A effential parts, but to fupply the want of a particular defcription, in your meaning, I, in the treatife, invited gentlemen, or a workman in each county, to give me a letter when my affiftance was wanted in a more minute direction.

N reading your magazine for October. I find you have done me the honour of taking notice of my Seed-furrow plough; but as you have mistaken fome particulars, I herewith fend you the following amendments of your defcription: I make little donbt of your inferting them in your next Ma-. gazine, otherwife you may prejudice your readers against what was intended for the use of country gentlemen first, and what may afterwards by them be reduced to a very fimple state, for common farmers, if they can be C perfuaded to ufe a feed-plough. Gentlemen are capable of ufing a machine fo contrived as to perform univerfally, with regard to the various forts and fizes of feeds; but common farmers. fhould, fuitable to their large business, have a very plain machine, eafily made, and only capable of fowing peas or D beans, and cleaning the ground while the crops are growing; and happy would it be for them and the nation, would they be prevailed on to do that. By this you may fully understand that the feed-plough you mention is not intended for common farmers, and fo E much is often faid, and oftener implied in the body of the treatise.

When you fay, I have "introduced Ba great deal of machinery to regu"late the quantity of feed that is to be "fown, and to fit the apertures to the "different fizes of feeds, from a grain "of mustard to a small potatoe," you will give me leave to obferve, that this great deal of machinery is nothing more than moving the three fliders up or down, according to the fize of the feed to be fown, and, if the owner chufes, fcrewing on a particular apparatus, done in the time a man can tell a hundred, when he would fow his feed at regulated distances in the furrows, tho not to a mathematical exactnefs; but if he does not defire to be fo very nice in pianting the feed at one, two, three, &c. inches from one another, the apparatus is ufelefs, and then he may give the ground more or less feed (as the ftate of the land as to its vigour or poverty may require) by the touch of his hand, in raising or lowering the three fliders. If any man can be found who is able to construct a machine upon a more fimple principle, to do fuch a variety of work, I fhall be the first man in the kingdom to rejoice at the real bleffing to the public. But as there must be a motion raifed, in order to carry round the wheel in the hopper, I know not in nature of a more fimple principle of action than making the trundle upon the axletree excite the motion within the hopper, which is effected by the revolution of a spindle running through the bottom of the hopper into it.

F

When you fay, "that fo many "movements must either render it too "beavy for the seedsman to lift, or "too light for the rough work it is to "perform," I muft beg leave to obferve, that the seedsman can easily lift it up by the handles, even when the hopper is quite full, which it need never be without his confent; and that it is not too light for any foil you perhaps will believe, when I obferve to you, I had the stiffelt land in view when I conftructed the dimensions of the drills, and every part of the ma- G chine, because I formerly found my mistake in using machines of my own contrivance, which were either too light or too heavy.

Had I been as particular in describing the minute parts of the plough as you mention I ought to have been, I agree with you that workmen would have a clearer light to go by; this I was undoubtedly aware of, as I know the trouble I have had in reading the defcriptions of all the drill ploughs hitherto known; but then, Gentlemen, from fuch a minute defcription,

H

Your defcription of the cones, &c. within fide fhould amount only to this; there are two cones whose business it is to throw down the feeds, (in order to guard against their propenfity to arch in their defcent) into three boxes, before which the diagonals appear in their gentle motion round, and which carry off the feeds to the apertures, and there difpofe of them into the fpouts. There is nothing difficult in all this, notwithstanding e formidable appearance?

516

Defcription of a Remarkable Fish. (See the Plate.)

the description; and I believe, nay
ampofitive, with a very little acquaint-
ance with the original, it will be
thought easy to be understood, and
fimple in the parts. I muit own, I
am forry there were any pains taken A
to plant the feeds of beans, wheat,
rapes, turnips, &c. in fome fort of re-
gularity from feed to feed in the fur-
rows, because this apparatus makes a
confiderable addition to the drawings,
and is apt to perfuade fome other rea-
ders, as well as you, that the plough is
not fo plain as they could wish.

B

An Account of a remarkable Fish, taken in
King Road, near Bristol: In a Letter
from Mr James Ferguson, to Thomas
Birch, D. D. Secret. R. S.

T

Briftol, May 5, 1763. HE length of the fish is four feet nine inches, and the thickness in proportion as in the figure. The mouth is a foot in width, and of a fquarif form: It has three rows of fharp fmall teeth, very irregularly fet, and at fome diftance from each other: it has no tongue, nor narrow gullet, but is all the way down, as far as one can fee, like great hollow tube: In the back of the mouth within, there are two openings like noftrils; and about nine inches below the jaw, and under thefe openings, are two large knobs, from which proceed several fhort teeth; a little below which, on the breaft fide, is another knob with fuck teeth.-On each fide within, and about a foot below the jaws, there are three cross ribs, fomewhat refembling the ftreight bars of a chimney-grate, about an inch distant from each other; through which we fee into a great caDvity within the fkin, towards the

When you fay "it has not been af "certained whether the plough will "anfwer in practice," you will be pleafed to understand it thus; the plough confifts of two principles; one working in the upper hopper, and is not new to me, as it has fown me many an in- C closure, and in the most effectual man. ner, with fome of the common feeds, but now improved to be universal and eafy; the other, working in the lower hopper, is both univerfal and easy, and has been put in practice privately to regulate the quantity of feeds to be thrown out; fo that a gentleman has the choice of two principles to effect the fame thing.

The fociety to whom the treatise is dedicated, having given till the latter end of next year to produce certificates of the plough's performances, I have all thofe featons to fow the various feeds in upon my hands, to exhibit its ufe before numbers of judges; not but I have been many times earneftly bent, during the present year, upon using the plough publickly, and before the treatife was printed off, but I have been as often difappointed by the abominable delays of the workmen when there was any alteration to be made, after many of thofe private trials.

Whoever the gentleman in my neighbourhood was, whom you confulted, I know not, but he was only defective in his information in not faying, it has not been publickly tried. But as I fhall, in all next year, give proofs of what I have faid of the plough, fo, when the public is fatisfy'd, I may fend you the various experi

ments made in the different feedtimes, till after the wheat is fown, as there appears fome benevolence in you in defiring a plough made under my eye, that you may excite the public to carry it into practice.

I am, Sir, withing continual fuccefs to your excellent Magazine, Yours, York, Nov. 13, 1764. J. RANDALL.

E

F

G

breaft; and under the skin, these cavities are kept diftended by longitudinal ribs, plain to the touch on the outfide. I put my arm down through the mouth, quite to my shoulder, but could feel nothing in the way; fo that its heart, ftomach, and bowels, mult lie in a very little compass near its tail, the body thereabout being very small.

From the neck proceed two long horns, hard and very elaftic, not jointed by rings as in lobsters: And on each fide of the back there are two confiderable fharp edged rifings, of a black and long fubftance. Between each eye and the breaft, there is a cavity fomewhat like the infide of a hu man ear; but it doth not penetrate to the infide. From each fhoulder proceeds a strong mufcular fin, clofe by which, towards the breast, is an opening, through which one may thruft his hand and arm quite up thro' the mouth: And between thefe

fins proceed from the breast two fhort paws, fomewhat like the fore half of à human foot, with five toes joined together, having the appearance of nails. Near the tail are two large fins, one on the back, the other under the H belly. The skin is of a dark brown colour, but darker fpotted in several places, and entirely without fcales.