HARDNESS. : 
with Certain eats; and a repulfion’ with the oppofite parts. fpecifie gravity of bodies ; fora diamond, the hardeft fub. 
_ ‘Hence, when they are placed jn fuch a fituation as may {tance in nature, is little more than half as heavy as 
allow them to follow that natural inclination, viz. when the All bodies are mente by cold; but fome 
are rendered fluid by heat, or by folution in water, &c. then become hard by heat as well as by cold. ye water be- 
they adhere to each other with their friendly parts: Alfo, comes hard by.cold, when it is Se ; but it becomes much 
when the operation proceeds flowly, the particles have more harder when its fteam is paffed over red-hot iron, and it 
_-time to arrange themfelves properly, and confequently form enters the fubitance of the metal by an union with which’ 
a harder body than when the operation proceeds more ex- it becomes almoit as hard as glafs. 
peditionfly. (Higgins on Light.) *See Conxsion and We fhall here fubjom fome obfervations, refpecting the 
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stic Bodies. hardnefs of different fubftances. The metals may be claffed, 
The Peripatetics make hardnefs a fecondary eee as according. to Cavallo (Philofophy, vol. it.) with refpe& to 
fuppofing it to arife from drynefsy which i is a primary o bardnels, in the following order, beginning with the hardeft 
o be in proportion to it. ending with the fofteit ; iron, platina, copper, filver, 
Its remote caufes, according to S tine are = aiahen heat or oak tin, and lead. ‘The order of the femi-metals is as 
ie perene to the diverlity of the fubject: heat pro- follows; m manganefé, nickel, bifmuth, tungften, zinc, an- 
ynefs, and by that means hardneis in clay; and timony, and arfenic. Stéel may be rendered harder 
ah Sa ee the like in wax. any other metallic fubitance. ‘Thus, ifa piece of fteel be 
The Epicurean and baepofculse philofophers account for heated red-hot, and in.this {late be plunged in oil, it will 
hardnefs, fon the figure of the component parts, and their become fo hard, that a file will hardly feratch it; and it will 
union together. Accordingly, fome afcribe it to the atoms, be rendered ftill harder, if, inftead of oil, the inky hot fteel be 
or particles of the body being hooked, and thus mutually plunged in water ; but if cold mercury be ufed inftead of 
catching and hanging upon one another: but this is dire@ily either oil or water, then the fteel will be-rendered fo hard 
shag that for an anfwer, which was the queflion. For as to fcratch glafs nearly as well as a diamond, The hard- 
w do thefe hooked parts cohere? nefs of other natural folids, befides the metals, differs con- 
a hats the Cartefians will have the cohefion of Les bo- fiderably, according to the ftate of purity and various other 
dies effected by reft ; that is, by nothing at all. circumftances. An ufeful gradation of the principal natural 
Sir Lfaac Honea fhews, that the primary particles of all folids, with refpeét to hardnefs, is exhibited 1 in the following 
bodies, whether folid or fluid, are hard, perfeGtly hard ; rasa rca from M. Magellan’ $ edition of Cronftedt’s 
and are not capable of being broken or divided by any power Mineralogy, which was taken from Quift’s tables, from 
nature. Be sea: and from Kirwan. The firit column fhews t 
_ Thefe parti icles he maintains to be connected together by a aia and the ieee the de gravity. 
Diamond 
.an attractive power; and according to the circumitances from Orm : = Sieg td gee 
= gs attraction, the body is either hard or foft, or even _ Pink, aR se Arar - - igi 2 56 
Blueifh. diamond eee +i 0;* IQs ores 
“TE the particles be fo difpofed or wl for each other, as Yellowith diamond —- - = ee ee 
_ to touch in lar rge furfaces, fuch body will be hard; andthe . Cubic diamond - - - ° 18: BF 
more ae as thofe furfaces , onthe con- Ruby < - - < oat, eee 
4 y only touch in fmall { eS, body, by the Pale ruby from Brazil = - + - 104.289 
. nels es the attraction, will remain in fof.’ See ConExsion. Ruby fone) 5. = ess us, tee 
ity has been found by the experiments of fome mo- Deep blue fapphire - ee eee 16, 2a 
a chemifts and philofophers, to confift in the motion of | Do, paler - Eee ee ~t, (tle ae 
ie Panic of a body upon one another in confequence of opaz - * - - - LS 
a fluid, confidered as uniyerfal and denominated Whitifh do . - - - > 14 33 
phar ba fire ; and hence it has been concluded, that hard- Bohemian dos -. = ae SAS eee 
nefs confilts in abfence or deficiency of that element, © Eme aie Rs Se - +23 34 ae 
called “ latent heat.” This is principally obferved inthe Garnet -. - -  - -  -. 32 Af 
metals, and hence refults their du@ility ; which property, ~ Agate = * - - - — at ae ae 
_ as well as fluidit depends altogether ona certain quantity . Onyx - .- 9+ = «5 1% 12, an 
of latent heat Y ablaked. or acting within the fubftancesthem-  Sardonyx - - - wf eer £2 eG 
_- felves'; for all metals are rendered hard by hammering, and. Quid. amethyft - eye ge i tee 
oft by being .again: kept for fome time in the-fire. The, .Cryilal — - a ae ae a es ere 28 
: former operation renders them hot as well as hard; probably, Cornelian - © - - , = *~- «2 = HES, eT 
‘fiys Dr. Black, becaufe the particles of metal are thus Gum jafper mie < og ake Cee 
omer one another, and thofe of fire fqueezed out a —— < ome - - 4 +e 
among them. By keeping them for fome time in the hoerl - - - - - 10. 13. 
re, that element pate infinuates. aie among the particles, yee ve Sige bona” eg se as See 
oo antes the fame arrangement: as they had before, and itis es ee ee 10 | of 3 
thus t v ductility aoe By a nak hamm a os oe oe eo, 
property ts again deftroyed, returning on a repetition of the —_Chryfolite - a eer ee 10 31 
eating or fen efs, it is faid, a eolite . <! — ogre Bo) 
- diminith the cohefion of bodies in fome degree. Though, or. eo et oe ee oe 
their agin ‘does not correfpond with their hardneis. Calcareous ee ee ee = 3 ‘hemes 
. Glafs is hard, but very piri whereas. flint, though  Gypfum = ie ea oa ee Bes a es] 
-harder than glafs, is much lefs brittle. With ——— to . Chalk eee “dedet 
metals, Bower ae is different ;, for feel, the hardet _ N, B..T eta eS as rae fa osiving the: 
oF the pis ens is the moft brittle, but lead,. the fofteit, is in which different fubifances are adaj ib a or make “any 
ft, the molt: dafble, ES Renee Semen ith He inch Meret: ag - HARDO! 
cle Rees Sigitcey e <A sic 
