12 MODERN SCIENCE READER 



the bits which fall from the horse's hoof as it is being shod 

 by the farrier make a most valuable dye when mixed with 

 certain chemicals and metal scraps. 



Over nearly every large city, especially such centers as 

 London, Birmingham, and seats of other great countries, 

 are enormous clouds of smoke, which so frequently darken 

 the atmosphere that even at noontime it is necessary to have 

 lights in the buildings. Yet this smoke if properly treated 

 can be actually dissolved into several most useful elements 

 and the inventor has designed apparatus by which these 

 elements can be secured at a small cost. It is a fact that 

 smoke can be weighed and measured like so much earth 

 and sand. Experiments which have been made in the 

 United States show that a cord of ordinary fuel wood in 

 burning generates 28,000 cubic feet of smoke. If the 

 smoke from one hundred cords of wood is treated by this 

 process, it will yield no less than six tons of the valuable 

 chemical known as acetate of lime, besides twenty-five 

 pounds of tar. But the smoke contains so much of the 

 elements of alcohol, that this quantity will produce no less 

 than two hundred gallons of spirit suitable for lighting, 

 heating, or the operation of motors. 



Usually perfumes and other useful odors are considered 

 as being obtained principally from flowers. The oils com- 

 ing from waste fruit, such as decayed pears, grapes, and 

 peaches, however, can be substituted for some of the most 

 costly floral odors after being treated with acids and other 

 liquids which give them a remarkable fragrance. Perfume, 

 soaps, even confectionery, are now manufactured, which are 

 flavored with what is called the oil of bitter almonds, but 

 which is extracted from the tar which is a refuse of gas- 

 making plants such as are to be found in every large city. 



The enormous production of iron and steel in various 

 forms has caused great furnaces to be erected for smelting 

 this metal in large quantities. Here again a study has been 

 made of what can be done to use what was formerly waste. 

 Even the gas which in the past has been allowed to escape 



