Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/867

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to move with it, were likewife increafed ; and thence it ne cefl'arily happened, that the afiion of the power was not fole- ly employed in giving motion to the impelled body, but much the greater: part of it was fpent in accelerating thofe parts of the machine in which the power refided, to enable them to purfue the body to be projected with perpetual impulfc. during its whole paffage through the extent of their activity Hence then it came to pals, that, though thefe antient ma- chines could throw enormous weights, they could project them but with fmall degrees of celerity, compared with what we can communicate to our cannon and mufket-fhot; whence in all operations, where thefe great velocities are ufeful, our ma- chines are infinitely fuperior to thofe of antiquity ; although, in more confined and fhorter projections, thefe iaft have fome' advantage which may yet render them worthy of the attention of thofe military geniufes, who have capacity enough to con- fider each part of the profeflion according to its true and ge- nuine value, independent of the partial eftimation of the times they live in. Ibid. p. 55.

Powder being a mixture of fulphur and charcoal, which are very inflammable fubflances, with falt-petre, which in itfelf is not, if the falt-petre be too much in quantity, when com- pared with the other two, their burning may not be fufficicnt to confume the whole of the fait-petre ; whence the fire may be lefs violent, and confequently the powder lefs vigorous, than if fome of the falt-peter was taken away, and a like quantity of the other materials were added in its flcad. On the other hand, if the falt-petre in the compoiition be lefs than what the burning of the other two fubflances can eafily confume, the fire will be lefs active than it ought to be, be- caufe it is not augmented fo much as it would be if a large quantity of falt-petre had been added to the compofition. Hence it appears that the goodnefs of powder is not to be eftimated only from the quantity of falt-petre contained in it, although that fubftance feems to be the bafis of the elaftic fluid, in which its force conMs. For fince the converting of the falt-petre into that fluid, and the elafticity of the fluid, afterwards, depend in fome meafure on the violence of the fire produced at the explofion, it is plain that there is a cer- tain proportion in the mixture of the materials, which wilt fceft contribute to this purpofe, and confequently to the per- fection of the powder.

What this proportion is, has been afcertained by experience, and it feems now to be generally agreed, that in any quan- tity of powder J of it mould be falt-petre, the remaing ^ confining of equal quantities of fulphur and charcoal. This is the proportion followed by the French, and by moft na- tions in Europe : we, indeed, pretend to a greater degree of nicety in our proportions ; though, it is faid, they do not greatly differ from what is here mentioned ; nor is it certain that they are preferable : this however may be depended on, that no methods of proving powder, hitherto generally practif- ed in England, could at all afcertain the difference ; and other powders made with the ufual proportions, are nothing inferior to ours. Ibid. p. 62.

But it is not the due proportion of the materials only, which is necefl'ary to the making of good powder ; another circum- ftance, not lefs ejTential, is the mixing them well together ; if this be not effectually done, fome parts of the compofition will have too much falt-petre in them, and others too little and in either cafe there will be a lofs of flrength in th- powder.

As the excellence of powder then depends on fo many par- ticulars, in the quality and quantity of the materials, and in the working them together, it is, doubtlefs, of great import- ance, that thofe who receive the public ftores lhould have it in their power to fatisfy themfelves about the goodnefs of what is delivered to them. The method moft commonly followed for this purpofe, here with us, fays the author above quoted, is to fire a fmall heap of it on a clean board, and to attend nicely to the flarne and fmoke it produces, as likewife to the marks it leaves behind it on the table ; from all which in- firuflive particulars the merit of the powder is afcertain- ed with great accuracy, as is pretended ; but befides this un- certain method, which, how much foever it may be praciif- ed, none will undertake ferioufly to defend, there are, on particular occafions, other contrivances made ufe of, all which bear fome analogy to the common powder-triers, fold at the fhops : only they are more artfully fabricated, and inllead b( a fpring they move a weight, which is a more certain and equable power.

But thefe machines, though more perfect than the common powder-triers, are yet liable to great irregularities; for as they are all moved by the inftantaneous ftroke of the flame, and not by its continued preffure, they do not determine the force of the fired powder with that certainty and uniformity which were to be defircd in thefe kinds of trials : and there- fore, the method followed by the French, in the receiving of powders from the makers, feems to be rnuch better. Their practice is thus :

They have, in each magazine, a fmall mortar caft with its bed, according to a determined pattern, which is the fame throughout the kingdom : this mortar is always pointed at

GYM

45°> and it contains juft three ounces of powder ; and it is a Itandmg maxim, that no powder can be received into their ftores, unlels three ounces of it, placed in the chamber of this mortar, throws a folid ball of 7 f- inches diameter to ti« dilrance of at lcaft 55 French fathom. But if each barrel' of powder was to be proved in this manner, the trouble ol" charging the mortar, C3Y. would be intolerable, and the de- lay fo great, that no bufinefs of this kind could ever be Siiifl]. ed. 1 he method by firing againft a pendulum, in the man- ner mentioned under the head Gunnery-, feems a readier way ; but ftill it requires fome nicety and time, which it Were to be wifhed could be obviated. Ibid. p. 63. It has been obferved that a heap of gun-powder of a certain diameter being fired, will always fet fire to another heao not diftant from the former above eight times its diameter. Perfons keeping more than 20olb. weight of gun-powder at one time, within the cities of London and Weilminfter, or their fuburbs, (3c. are liable to forfeitures if it be not re- moved ; and juftices of peace may iflue warrants to fcarch fois feize, and remove the fame, 5 and 1 1 Geo. J. and 5 Geo. II. cap. 20. GURGIPTING, in falconry, a term ufod when a hawk is ftifF

and choaked up. Ruft. Diet, in voc. GUTTA rofacea, in medicine, denotesa red or pimpled face; a diftemper, which, tho' not always owina its original to hard drinking, is jicverthclefs moft incident to tiplcrs of ftrong beer, wines, ipirjts, ISc.

As to the cure, befides making a revulfion by bleeding, blif- tering, cupping, iflues, tJV. the diet ought to be moiftening and cooling, as lettuce, purflain, forrel and fpinach : the drink may be an emulfion of the cold feeds, milk and water, clarified whey, &c.

In the ufe, however, of this cooling regimen, great caution is neceffary ; for if a perfon be taken off at once from his ftrong liquors, and allowed nothing but whey, or milk and water, it may coft him his life, by haftening a fudden de- cay of heat, palling his appetite, and bringing on a leuco- phlegmatia, or dropfy. James's Medicinal Dictionaryi in voc.

As for what concerns topics, much caution is likewife to be ufed. If there be only rednefs without pimples, and the difeafe recent, refrigerants and repellants take place : but if puftules appear, difcutients muff be mixed; and if thefe puftules feemhard, and the difeafe be of long Handing, there maybe reafon for emollients to ripen and digeft the tough and viltid matter, which is afterwards to be let out. Id. ibid. If the difeafe be ftubborn, and the tubercles grown hard, we are to begin with emollients, both fotus and ointment : fuch are the decoction of mallows, vervain, folomon's feal, and linfecd ; alfo a cerate of fperma ceti, or Bate's white cerate. Id. -ibid,' GUTTER (Cycl.) — Gutters are either parallel to the ho- rizon, or vertical. The former mould be made with a pro- per defcent, that there may be a good current, as the work- men term it ; for if laid too level, the water will be apt to Hand in plafhes,

As to the vertical gutters, or thofe formed by two roofs meet- ing at right angles to each other, or by the end of one roof joining to the fide of another, they are either made of lead, or tiles, which are either plain or concave ; thefe laft are call- ed gutter-tiks, and may be eafily laid. But in laying on the plain tiles the workman begins at one fide of the gutter, and fo works acrofs, as if it we're plain work, and then brings the next row of tiles back again ; fo that he works forth and back, to and fro, from right to left. By this means the gut- ters laid after this manner are no( angular, but of a kind of diftorted curvilinear form, which prevents the mortar from. • being warned away with the rain. Build. Did. in voc GWAYF, or Waif. See Waif, Cycl. GYMNARTHRIDIA, in the hiftory of ipfefls, a feries or clafs of infects, which have foft and' naked bodies, furnifhed with limbs. See Insect, Append.

Thefe have been generally called zoopbytes, a term exprefflng creatures partly of an animal, and partly of a vegetable na T ture ; but as it is now well known that there are none fuch, U is proper the term zoophyte lhould no longer be retained. Under this clafs are comprehended the Umax, or the naked mail, the lernea, mtdufa, apbrodita, ampbitrite, (Sc. HUP, Hift. Anim. p. 87. See the articles I.imax, Lernea, istc, Append. GYMNOSOPHISTS (Cycl.) — There were likewife African gymnofnpb'ijh, who dwelt upon a mountain in Ethiopia, near the Nile, without the accommodation either of hottlc or cell. Thefe did not form themfelves into focieties, like thofe of India ; but each had his private retirement, where he ftudied and performed his devotions by himfelf. If any perfon had killed another by chance, he applied to thefe fages far abfo- lution, and fubmitted to whatever penances they enjoyncd. They pretended to an extraordinary frugality, and lived only upon the fruits of the earth. Lucian afcribes to thefe phllo- fophers fevcral new difcoveriet in aftronomy, Brougbton, Diet. Reiia. in voc.

GYMNLA,