HORNS AND HOOFS. 327 



usually carried on in the following way : large quantities of 

 fresh blood — from two to three tons at the time — are filled 

 into wooden or iron tanks of suitable size, containing double 

 bottoms several inches apart. The upper (or false) bottom 

 is thoroughly perforated by numerous small holes, and cov- 

 ered over with coarse sacking to serve as a filter. 



The two bottoms have also one larger communicating hole, 

 which is closed with a well-fitting stick reaching to the surface 

 of the vessel. The latter is used for the discharge of the 

 liquid which has passed through the filter after the treatment 

 of the blood has ceased. 



A suitable steam-pipe passes directly down to the filter. 

 The excess of the steam is controlled by a wheel-valve fas- 

 tened in the pipe somewhere near the boiling vessel. As 

 soon as the latter is charged with blood, the steam is turned 

 on for about one hour. During this time the liquid is contin- 

 ually agitated. The nitrogenous or albuminous mass of the 

 blood, which in consequence of that operation has become 

 coagulated and has formed a flocculent mass, is collected upon 

 the filter, after the liquid has been discharged, and subse- 

 quently dried by steam. The amount of nitrogen lost by dis- 

 charging the liquid portion does not exceed one-half of one 

 per cent, of the entire quantity present. 



Ground Horn and Hoof. 



The substance submitted to an analysis was of a grayish 

 yellow color, and in a fine pulverulent condition ; it contained 

 15.49 per cent, of nitrogen. This highly nitrogenous fertil- 

 izer, which but recently has been introduced into our markets, 

 is usually prepared in the following way : the pieces of horn 

 and hoof are filled into a cylinder similar to those used for 

 steaming bones, and subjected for several hours to the action 

 of steam of from two to three pounds' pressure. According 

 to the size of the material treated, the time is extended or 

 shortened. 



The horn, after being properly treated, is soft, like rubber ; 

 dried by hot-air it becomes brittle, and is easily ground into 

 a fine powder, which decays quite readily in moist soil. Hair, 

 refuse wool, feathers and whalebone are of a similar composi- 



