M. TECHNOLOGY. 549 



its transparency. Of two others, subsequently exposed, one, 

 treated twice a year with olive-oil, in addition to daily sprink- 

 ling with water, was greatly superior in brilliancy and clear- 

 ness to the other, w^hich had been simply sprinkled ; so that 

 mere cleansing in the w^ay indicated seems highly beneficial. 

 Two bronzes that had been artificially coated w^th patina, 

 and subjected to similar treatment fiar several years, presented 

 so satisfactory an appearance as to incline the committee to 

 recommend the use of artificial patina. 14 (7, 1872, ccvi., 200. 



WATER-PROOF PASTEBOARD. 



One of the cheapest and most effectual coverings to render 

 wood perfectly water-proof and increase its durability, and 

 which wuU impart to pasteboard the appearance and strength 

 of wood, is that employed in many ways by the Chinese, ac- 

 cording to tests made with a sample sent from Pekin by Dr. 

 Scherzer. It may be prepared, as a slightly viscid fluid fit for 

 immediate use, by stirring into three parts of fresh serum of 

 blood (or defibrinated blood) four parts of dry-slaked lime 

 and some alum. It should be laid on twice, or at most three 

 times, in order to render articles perfectly w^ater-proof. 10 

 C^ September^ \^1 2, IZS: 



TREATMENT OF HAIR FOR FELTING. 



Nitrate of mercury has for a long time been used in pre- 

 paring hair for felting, in the manufacture of felt hats, etc. ; and 

 numerous cases of poisoning are on record among the twenty 

 to thirty thousand Europeans engaged in this business. Ac- 

 cording to M. Hilairet, if the skins be impregnated with a 

 neutral substance, such as molasses, dextrine, or sugar, and 

 then placed in nitric acid, the hair undergoes a change of 

 structure by the action of the nitrous and hyponitric acids 

 thus developed, corresponding exactly to that obtained by 

 means of a solution of mercury in nitric acid. 15 A,A2)ril, 

 1873,281. 



REMOVAL OF OILY MATTER FROM W^OOL, ETC., BY HYDRO- 

 CARBON VAPOR. 



According to Simonin and Coffin, by passing vapor of any 

 of the light hydrocarbons produced in the rectification of 

 petroleum (as n-aphtha, etc.) througb wool, horse-hair, feathers, 



