460 FARMERS' INSTITUTES. 



mill. We have seen tliat the horse can do work that is equal to two-thirds 

 or 67 per cent nearly of a horse-power by traction alone. Nystrom says 

 that in a tread-mill, at a speed of three feet per second, a horse can 

 exert 57 per cent of horse-power, and at a speed of nine feet per second, 

 he can exert only 16 per cent of horse-power measured in pounds lifted feet 

 per minute. 



It is frequently claimed by salesmen of machinery that by means of their 

 machines more power is developed than is supplied to the machine. This 

 may be made to look reasonable by the specious words of an agent or even by 

 watching the machine itself, when nothing definite is known of the power 

 supplied. This doctrine is, in reality, more preposterous than that of per- 

 petual motion, for it not only assumes that no power is required to run the 

 machine, but that besides, runniug ihe machine, it actually does work in 

 addition. It is true that more work may usually be done with a machine 

 than v/ithout it, but that is because the power is applied to so much better 

 advantage, as to more than compensate for any lo?s. 



TBE SCIENCE OF CLAY-WORKING. 



BY PROF. R. C. CARPENTER. 

 [A Paper read before the Michigan Brick and Tile Association.] 



In talking on the above subject, I lay myself open to the charge of 

 speaking about something which does not exist. It is something, however, 

 which should exist, and no doubt the day will come when we shall be able to 

 foretell results as to character and kind of ware with positive and absolute 

 certainty, merely by analysis and examination of the clay. 



As is well known, the art of working clay so as to make brick and pottery 

 is the most ancient of arts, at least it dates back long before historic periods. 



We neither know the name of individual or of nation who made the first 

 bricks. We find that they were made in the earliest times by nations in all 

 portions of the world. They were made in Egypt, Mexico, Peru, and China 

 ages and ages ago. More than that, it is doubtful if, with all our improve- 

 ments in civilization and in manufacture generally, we can make brick equal 

 in quality to those made in Assyria and in China three thousand years ago. 



The methods used in Egypt were in that day as now, only crude, while we 

 are in total ignorance respecting the methods in other countries. This much 

 we know, however, the brick made in those days was often enameled or 

 covered with porcelain and rivaled our best attempts in clay working. The 

 art of burning, judging from the bricks, was well understood. 



The important operation of tempering, which is often entirely omitted in 

 our practice, was considered of so much importance by the ancient Chinese, 

 that the son worked the clay prepared by the father, and he in turn prepared 

 a stock to be worked by his posterity after he should have passed from this 

 life. This, no doubt, would be considered thorough work, but it is much 

 too slow for people of this age and generation. It is not my purpose to talk 



