PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 385 



dissolving- the butter out of the milk b}'- means of benzole, and measuring 

 the reduction in the volume. It consists you see of two glass bulbs, con- 

 nected by a hollow cylindrical stem. I fill the lower bulb and the stem 

 with milk, letting the milk rise in the stem to the zero mark. I then pour 

 a quantity of benzole into the upper bulb, when, by inverting the instru- 

 ment, the milk and the benzole are mingled together. I shake the mixture 

 so as to bring all portions of the butter into contact with the benzole, and 

 then re-invert the instrument. The benzole, being of less specific gravity 

 than the milk, rises to the surface, carrying with it the dissolved butter; 

 and the extent to which the surface of the milk descends in the cylindrical 

 neck indicates the quantity of butter extracted. As good milk contains 

 about four per cent, of butter, if I find that but two per cent, is tfrken out, 

 I conclude that the milk has been watered one-half. I have tried some 

 milk in this instrument from the same sample of some that I recently 

 analyzed, and I find that its indications correspond very closely with the 

 results of my analysis. 



Mr. Smith. — There is one difficult}'' with this lactometer and with all 

 others. Pure milk as it is drawn from the cow varies so much in quality 

 that ascertaining the quality, by whatever means, is no test of the purity. 



Mr. Fisher. — As it is the quality which interests us, and not the purity, 

 this would seem to be no objection to a good lactometer. 



Paper and its Manufacture. 



Mr. Smith. — I introduced this subject, with a view not of imparting 

 information, but of obtaining it. I will, however, make a few remarks to 

 open the subject. Paper is made of vegetable fiber, and it seems that 

 almost any vegetsible fiber answers the purpose. The first step, and ono 

 that costs a good portion of the labor, is to get the fibers separated. To 

 effect this the material is ground in mills and macerated in water, reducing 

 it to a fine pulp. It is then formed in sheets by different processes, 

 two of which are principally employed in this country. One of these is 

 the Fourdrinier, which was invented in France and perfected in London. 

 In this an endless web of wire cloth is run through the vat of pulp, picking 

 lip the pulp and carrying it off in a sheet, which is pressed between rollers, 

 and then dried. The other is calied the cylinder process. In this the pulp 

 is formed on a perforated hollow cylinder from which the air is exhausted, 

 so that the pressure of air upon the outside against the perforated cylinder 

 holds the sheet of pulp upon the surface. 



The Secretary explained the essential condition in the preparation of the 

 material to preserve the fibrous condition of the matter. Grinding it to 

 dust ruins it, and even reducing its fibrous condition beyond a certain 

 degree, gives it an undesirable character. He remarked on the fact that 

 matter seems in paper-making to conform to a law not found in general 

 manufactures, i. e., that while a moderate subdivision will not change the 

 character of rags, a fine division will cause the particles to cement them- 

 selves together, without the addition of any substance, into a hard material 

 called paper, essentially different in its character from rags. He said "half 

 stuff," or paper stuff, partly beaten, was soft and rag-like, but the same 

 pulp beaten in pieces or just suflSciently beaten to be proper " stuff, " would, 



[Am. Ixst.] 25 



