Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/870

 HEA

HAZLE,oi-Haz.ei. (Suppl.)— {fltch-BAiLE, anamefometimes ufed for the Ubruu, or Elm. See the articles Ulm us and Elm, Suppl.

HEART-iarn. In furfcits, or upon fwallowing without due maltication ; when meats are eat tough and fat, or with fari- naceous fubftances unfermented ; or when by any accident the faliva is vitiated, too fcanty, or not intimately mixed with the food, the fermentation becomes tumultuous, the fto- mach fwells with air, and this extraordinary commotion being attended with an unufual heat, brings on the uneafinefs called the heart-burn ; which is remedied by whatever promotes a greater fecretion of falvia, or helps to mix it with our ali- ment. Pringle, Obferv. on the difeafes of the army, p. 168. See the article Fermentation, Append.

HEART's-ra/S, a name fomctimes ufed for a fpecies of violet, otherwifc called Pan/ay. See the article Violet, Suppl. It is faidtobegood for ruptures and the falling fickncfs. Ruft. Diet, in voc.

"HEAT (Suppl.) — Heat is found to expand and dilate metals confidcrabiy, as uppears from an experiment of Mufchenbroek, who tells us, that having prepared cylindric rods of iron, fteel, copper, brafs, tin, and lead, he expofed them firit to a pyro- meter with two flames ; then fncceffively to one with three, four, and five flames. But previous to this trial, he took care to cool them equally, by expofing them fome time upon the fame ftone ; when it began to freeze, and Fahrenheyt's thermometer was at 32 degrees. The effects of which expe- riment are digefted in the following table, where the degrees of expanfion are marked in parts equal to the n ; !B part of an inch.

Expanfion of

I Iron I Steel | Copper | Brafs | Tin ] Lead

By one flame

I 80 I 85 I 89 I no I 153 I 155

By two flames, placed clofe together

117

'23

"5

220

2 74

By two flames 2 I- ( inches diftant

109

9+

92

141 1 219 |

263

By three flames placed clofe together

142

168

'93

2 75

By four flimes placed clofe together

.

211

270 1

361

1

By five flames | 230 j 310 J 3 10 | 377 1 1

It is to be obferved of tin, tbat it will eafily melt, when heated by two flames placed together. Lead commonly melts with three flames, placed together, efpecially if they burn long.

From thefe experiments it appears at firft view, that iron is the leaft rarified of any of thefe metals, whether it be heated by one or more flames ; and therefore is raoft proper for mak- ing machines, or inftruments, which we would have free from any alterations by heat or cold, as the rods of pendulums for clocks, £3V, So likewife the meafures of yards or feet fhould be made of iron, that their length may be as nearly as pofflble the fame, fummer and winter.

The expanfion of lead and tin, by only one flame, is nearly the fame ; that is, almoft double of the expanfion of iron. It h likewife obfervable, that the flames, placed together, caufe a greater rarefaction, than when they, have a fenfible interval between them ; iron, in the former cafe, being expanded 117 degrees, and only 109 in the latter j the reafon of which difference is obvious.

By comparing the expanfions of the fame metal, produced by one, two, three, or more flames, it appears, that two flames do riot caufe double the expanfion of one ; nor three flames three times that expanfion, but always lefs ; and thefe expan- fions differ fo much the more from the ratio of the number of flames, as there are more flames acting at the fame time. It is alfo obfervable, that metals are not expanded equally, at the time of their melting, but fome more, fome lefs : Thus tin began to run, when rarified 219 degrees; whereas brafs was expanded 377 degrees, and yet was far from melting. Defagul. vol. 1. p. 423, feqq. Heat, in Medicine. Great Heats are not fo much the imme- diate, as the remote caufe of a general ficknefs, by relaxing the fibres, and difpofing the fibres to putrefaction ; efpecially among foldiers, and perfons expofed the whole day to the fun; for the greateft heats are feldom found to produce epi- demic difeafes, till the perfpiration is flopped by wet cloaths, fogs, dews, damps, &c. and then fome bilious or 'putrid diftem- per is the certain confequence, as fluxes, and ardent inter- mitting fevers. Neverthelefs, it mult be allow'd, that beats have fometimes been fo great, as to prove the more immediate caufe of particular diforders. As when centinels have been placed without cover, or frequent reliefs, in fcorching heats ; or when troops march, or are exercifec! in the heat of the day : or when people imprudently He down and ik-cp in the fun :

H E L

All thefe circumftances arc apt to bring on diftempers, varying according to the feafon of the year. In the beginning of fum- mer, thefe errors produce inflammatory fevers ; and, in the end of it, or in the beginning of autumn, a remitting fever, or dyfentery. Pringle, Obferv. on the Difeaf. of the army, p. 79, feqq.

To prevent, therefore, the effects of intemperate heat, com- manders have found it expedient fo to order the marches, that the men come to their ground before the heat of the day ; and to give ftri£t orders, that none of them fieep out of their tents ; which in fixed encampments may be covered with boughs, to fhade them from the fun. It is likewife a rule of great im~. portance to have the foldiers exercifed before -the- cool of the morning is over; for, by that means, not only the fultry heats are avoided, but the blood being cooled, and the fibres braced, tlie body will be better prepared to bear the heat of the day. Lafily, in very hot weather, it has been found proper to fhorten the centinels duty, when obliged to ftand in the fun. Id. ibid. p. 95.

HEATH (Suppt.) ~- Mowitai k-He at H, a name fometimes given to the Saxifrage of botanical writers. See the article Saxifrage, Suppl.

Berry-bearing Heath, a name fometimes given to a genus of plants, called by botantfts Rittpetnum'. See $ic article Empe- trum, Suppl.

Low-pine Heath, the name of a diftinct. genus of plants, called by botanilts Corts. See the article Coris, 'Suppl.

HECKLE, among hemp-drafters. See Hatchet., fupra.

HECTIC. See the article Consumption, Append.

HEDERA (Suppl.) ■ — Firginian-Hu d era, the name by which Piukenet calls the Menijpermum of Linnarus. See the article Menspermum, Append.

HEDGK-hog, in zoology, the Englifh name of a genus of ani- mals,. called by zoologiits Erimueus. See the article Erina- CEUs, Suppl.

Hv.DGE-hog, in botany, the Englifh name of a genus of plants called by botanifts Erinaeea, See the article Erinacea Suppl.

Sea Hl;dge-%, the Englifh name of a fcries of lhell-fifb called by different authors Ccntronia^ Echini inar'tni, Echino- dermata, &c. See Centronia, Append, and Echino- derma, Suppl.

Hebg E-hog-Medica, the name by which fome call feveral fpe- cies of Medica, or lucerne. See the article Medica Suppl. *

HEVGE-hog-thi/lle, a name fometimes given to a diftinct o-enus of plants, called by authors Cactus. See the article Cactus, '■ Append.

■ H-EDGE-hx/Jbp, a name fometimes given to a difrin£t genus of
 * plants, called by botanifts Digitalis. See the article Digita-


 * us, Suppt.

Hedge-w«/2W, the name of a genus of plants, known anions

botanifts by that of Eryfimum. See the article Erysimum?

Suppl. Hedg E-nettle, a name fometimes given to a genus of plants,

called by botanifts Galeopfts. See the article Galeopsis,

Suppl. Hevg E-nettle-Jbrub, a name by which fome call the Prafmm,

a diftmcT: genus of plants. See the article Prasium,

Suppl Hedg E-fparrow, the Englifh name of a fpecies of Motaeilla,

See the article Motacilla, Suppl. HEDIUNDA, in botany, a name ufed by fome writers for the

Cef.rum of Linnsus. See thearticle Cestrum, append. HEDYSARUM, in the Linnaian fyftem of botany, the name

of a large genus of plants ; which that author makes to com- prehend the Hedyfarum, Onobrychis, and Jlhagi of Tourne-

fort. See the articles Hedysarum and Onobrychis,

Suppl. and Alhage, Append. HEEL, among carpenters, denotes an inverted Ogee. See the

article Ogee, Cycl. HE1NASE, among fportfmen, a roe- buck of the fourth year.

Ruft. Die!:, in voc. HELKGUG, in zoology, a name given to the Anas arclica. See'

the article Duck, Suppl. HELEN IUM, in botany, the name ufed by fome for feveral

fpecies of After, or ftar-woit. Sec the article Star-wort.

Suppl. HELIANTHUS, in the Linmean fyftcm of botany, the name

by which that author calls the Corona foils, or great fun-flower.

See the article SvK-flozucr, Suppl. HELICHRYSUM, in botany, a name ufed by fome authors

for the Gnaphalium, or cudweed. See the article Gnapha-

i.ium, Suppl. HELIOTROPE, in botany, the name by which fome call the

turnfol, a diftinct genus of plants. Sec the article Helio-

tropium, Suppt. Heliotropium is alfo a name ufed by fome for a fpecies-

of Ricino'ules. See the article Ricinoides, Suppl. Heliotropium is likewife ufed by fome for the" Hellanthus,

Corona folis, or great fun flower. See the article SxjN-Jlower,

Suppl. HELLEBORE, in botany, the Englifh name of a diftinct genus

of plants. See the article Helleborus, Suppl.

4 Bajtard-