BLE 



BLE 



direction corresponding with tho stra- 

 ta, and of greater or less dc|)th, ac- 

 cording to the material. The diame- 

 ter varies from one to one and a half 

 inches, as the rock is harder. Into 

 this is next placed a charge of pow- 

 der occupying aiiout one third of tlie 

 deiitli, ami furnished with a tin tube 

 containing the fuse or slow match. 

 After the powder, small pieces of rock 

 or paper are rammed, and then sand 

 is driven in, to fill the hole, and the ex- 

 tremity of the fuse lighted ; the work- 

 man retires to a place of safety, and 

 allows the explosion to take place. 

 In this way boulders, which impede 

 cultivation, and are too large to be 

 lifted away, may be broken up, and 

 the fragments removed for fences, &c. 

 Stumps of large trees may also be 

 torn up by blasting, the charge being 

 contained in a tin case, and introdu- 

 ced beneath the stump ; or the wood 

 maybe bored with an inch auger, and 

 the charge inserted into the wood it- 

 self 



BLATTA. The cockroach genus. 



BLAZE. A white mark or star in 

 the face of a horse or other animal. 



BLEACHING. This process con- 

 sists in a series of operations, by 

 which the natural colours of various 

 substances are discharged so as to 

 whiten them. It is effected either 

 by the action of various solvents, aid- 

 ed by exposure to light, air, and moist- 

 ure, upon the bleaching ground, or by 

 the aid of chlorine. Cotton is more 

 easily bleached than linen, in conse- 

 quence of its being originally whiter, 

 and having a less powerful attraction 

 for the colouring matter. In bleach- 

 ing these goods upon the old princi- 

 ple, warm water is first liberally ap- 

 plied to remove the weaver's paste 

 or dressing ; they are then bucked, or 

 boiled in a weak alkaline lye ; and 

 after having been well washed, are 

 spread out upon the grass, so as to be 

 freely exposed to the joint agencies 

 of light, air, and moisture ; the buck- 

 ing and exposure are alternately re- 

 peated, as often as necessary ; the 

 goods are soured, that is, immersed in 

 water slightly acidulated by sulphuric 

 acid ; lastly, they are very thoroughly 

 96 



washed and dried. By these opera- 

 tions the texture of the goods is, to a 

 certain extent, impaired, and much 

 time is required to complete the pro- 

 cess, which, also, cannot be carried 

 on in the winter months. But the 

 exposure upon the bleaching ground 

 is now, to a great extent, discontinu- 

 ed ; and the same efiect is obtained, 

 after the process of bucking, by the 

 action of weak solutions of chlorine, 

 or of chloride of lime, which, if skil- 

 fully used, can scarcely be said to in- 

 jure the goods more than the long- 

 continued exposure. The theory of 

 bleaching has not been satisfactorily 

 developed ; but, from such experi- 

 ments as have been made in refer- 

 ence to it, it appears to be a process 

 of oxidation, and to depend upon some 

 peculiar influence of nascent oxygen 

 upon the colouring matter. 



The colour of manufactured wool 

 depends partly upon its own oil, and 

 partly upon the applications made to 

 it in the loom. These are got rid of 

 in the fulling-mill by the joint action 

 of fullers' earth and soap ; the cloth 

 is then well washed and dried, and is 

 tolerably white ; if the slight yellow 

 tint which it retains is objectionable, 

 it is prevented by adding a little stone 

 blue to the washing water, or by ex- 

 posure to the fumes of burning sul- 

 phur ; this latter method, however, 

 gives it a harsh feel, and if afterward 

 soaped, its yellowishness returns. 



The colour of raw silk depends up- 

 on a natural yellow varnish, which is 

 got rid of by boiling it in white soap 

 and water, and by repeated rinsings. 

 Certain articles of wove cotton, such 

 as stockings, are bleached as usual, 

 and finished by the action of sulphu- 

 rous acid, or the fumes of burning sul- 

 phur. Straw is also whitened by a 

 similar operation ; and hence bleach- 

 ed straw hats are apt to have a disa- 

 greeable sulphurous smell. 



BLEACHING POWDER. Chlo- 

 ride of lime. 



BLEEDING. An operation fre- 

 quently necessary in the disorders of 

 different kinds of cattle, particularly 

 horses. Such horses as stand much 

 in the stable, and are full-fed, require 



