MECHANICS AND USEFUL ARTS. 59 



"It will not be necessary for me to dwell upon the filtering pro- 

 cesses required for large water-works, as the supply is generally 

 taken from such sources that the common sand filter-bed answers 

 the purpose ; and where the water is too hard for domestic uses, the 

 beautiful process of Dr. Clark will meet and .remedy the evil. 



" Experience shows that it is not prudent to adopt the same 

 means of purification for every kind of water, and I should make a 

 difference in the treatment of the water used for domestic and that 

 employed for manufacturing purposes. In the latter it will be often 

 of the greatest importance to have the water as pure as possible, 

 whereas certain so-called impurities in water may not be at all inju- 

 rious to health. When we consider that no one would call human 

 blood impure which contained four hundred and twenty grains of 

 saline matter per gallon, I do not know that we are justified (of 

 course, speaking in relation to health) in calling water impure which 

 contains small quantities of certain saline matters, particularly when 

 we have no medical evidence that the small portions of them drunk 

 in such water ever did any harm. Besides which, it should be re- 

 marked that the quantity of lime and magnesian salts drunk in water 

 must be greatly exceeded in amount by that which enters the sys- 

 tem in the food." 



Mr. Dahlke states that he preferred animal charcoal to all other 

 filtering media, and regretted that no practical method is yet known 

 Of moulding it into blocks without diminishing its powers. Char- 

 coal, he said, as regards its filtering qualities, stands to coke as fif- 

 teen to four, and all attempts at solidifying it by calcination with 

 pitch, tar, etc., have failed in practice, owing to the glazing effects 

 of the bitumen, which greatly impairs its action. He had, how- 

 ever, found that the residue, after distillation, of the well-known 

 Torbane-hill mineral, with a small addition of fine clay, will, if 

 saturated with fatty or oily matter, and calcined, furnish a very 

 powerful filtering medium, capable of reducing the hardness of 

 water, and removing; its color and odor. He also adds bone-dust, 



^j * 



both to improve the quality of the " filter-blocks," and in order to 

 regulate their degree of porosity with greater precision. 



SUBSTITUTE FOR GLUE VEGETABLE ALBUMEN. 



An improved process has been invented by E. J. Hanon, of 

 Paris, by which he obtains vegetable albumen from gluten, for 

 the purpose of applying it as a cheap agent for fixing printed colors 

 on textile fabrics, and also for uniting pieces of wood, leather, etc. 

 The following is the substance of the specification, as published in 

 Newton's London Journal of Arts : 



Gluten is obtained by kneading wheat flour paste with water. 

 During the operation of kneading, the feculent part of the paste 

 is carried off with the water, and the glutinous parts unite and form 

 an elastic substance called gluten, which contains about twice its 

 weight of water; the gluten, in this state, is converted into vege- 

 table albumen, by the process of fermentation. In carrying out 

 the invention, gluten of the best quality, free from fecula, and after 

 having been well washed in warm water, is placed in vessels, in 



