HEAT 793 



From the mixture of copperas and verdigris employed in the hat-dye, a vast quan- 

 tity of an ochreous muddy precipitate results, amounting to no less than 25 per cent, 

 of the weight of the copperas. This iron mud forms a deposit upon the hats, which 

 not only corrodes the fine filaments of the beaver, bu causes both them and the felt- 

 BtufF to turn speedily of a rusty brown. There is no process in the whole circle of our 

 manufactures so barbarous as that of dyeing stuff hats. No ray of chemical science 

 seems hitherto to have penetrated the dark recesses of their dye-shops. Some hatters 

 have tried to remove this corrosive brown ochre by a bath of dilute sulphuric acid, and 

 then counteract the evil effect of the acid upon the black dye by an alkaline bath ; but 

 with a most unhappy effect. Hats so treated are most deceptive and unprofitable ; 

 as they turn of a dirty brown hue when exposed for a few weeks to sunshine and air. 



HAUERXTE. A bisulphide of manganese, occurring at Kalinka in Hungary. It 

 is named after the eminent Austrian geologist, Von Hauer. 



HATrsiYXANTCXTE. Native proto-peroxide of manganese. See MANGANESE. 



HAUYNE, A mineral occurring in blue or green crystals and crystalline masses, 

 belonging to the cubic system, and presenting a complex constitution ; they consist of 

 a silicate of alumina, lime, soda, and potash, with sulphate of lime. 



HAWTHORN. (Epine blanche, Fr. ; Weissdom, Ger.) Cratagus Oxycantha, 

 Linn. This shrub has a hard whitish wood, but as it is small and difficult to work, it 

 is not much used. 



H AYE SINE. A borate of lime, which is found abundantly on the western coast 

 of South America, so called from its discoverer. It has been introduced for use in our 

 glass manufacture, and is used by our potters. See BORACIC ACID. 



HAYTORXTE. A pseudomorph of quartz after datholite, found at Hay Tor in 

 Devonshire. 



H AZEZi. (Noisetier, Fr. ; Haselstaude, Ger.) The Corylus Avellana, a small under- 

 wood, used a little in turnery and for the manufacture of toys. The nuts are eaten. 



H AZEZi. A North of England term for a hard grit. 



HAZEZi IVXOUXiD. The name given in Hampshire to a light loamy soil. 



HEARTH (Foyer, Fr. ; Heerde, Ger.) is the flat or hollow space in a smelting 

 furnace upon which the ore and fluxes are subjected to the influence of flame. 



HEARTHSTONE. A soft stone employed for whitening door-steps, &c. A 

 large quantity of hearthstones are brought to London from the quarries in the Upper 

 Greensand at Godstone in Surrey. See GREENSAND. 



HEAT. The Force or Principle upon which the conditions, relatively, of solid, 

 fluid, and aeriform states depend. That which produces the sensation of warmth. 



The discussion of the habitudes of heat with the different kinds of matter belongs to 

 physico-chemical science, and is treated of in Watts's ' Dictionary of Chemistry.' It 

 will suffice, in this place, to state succinctly those laws which have, more directly, a 

 bearing on any of our manufacturing processes. 



Heat and motive power are mutually convertible, and heat requires for its production, 

 and produces by its disappearance, motive power in the proportion of 77 '2 foot-pounds for 

 each Fahrenheit unit of heat. BanJcine. 



This unit of heat has been established by Dr. Joule to be the amount of heat re- 

 quired to raise the temperature of one pound of liquid water by one degree of Fahren- 

 heit. A falling weight, or any other mode of motion, produces a definite quantity of 

 heat according to this law. 



If the total actual heat of a homogeneous and uniformly hot substance be conceived to 

 be divided into any numbers of equal parts, the effect of those parts in causing work to be 

 perfor?ned will be equal. Eankine. 



Or, in other words, of a given equivalent of heat, from whatever source produced, 

 the work which it can effect is always an equal and constant quantity. 



Heat may be produced by friction, as we see in the development of it powerfully, 

 in the axles of railway carriages insufficiently lubricated. By the attrition of two 

 pieces of wood ignition can be obtained. 



Heat is developed in the mixture of bodies of different densities, such as spirits of 

 wine and water, or sulphuric acid and water, there being a diminution of volume in 

 each case. 



Heat is produced by many conditions of chemical combination, in numerous cases 

 so energetically as to produce intense combustion and even explosion. 



Heat is obtained by combustion for our ordinary manufacturing processes, and 

 domestic uses. This is a chemical union of one body with another, as carbon with 

 oxygen ; but to effect this, an excitant appears necessary or a continually increasing 

 excitement of the energy upon which heat depends, as, the application of flame in 

 one case and the phenomena of spontaneous combustion in another. 



Electricity by its disturbing power, developers heat, and this all-important force is 

 also rendered manifest by the processes of vitality (vital or nervous force). 



