198 Alia hpei of Books. [March, 



if the demand for the particular kind of goods they were weaving 

 should change or fall off. 



Such is a sketch of tlie historical facts contained in this inte- 

 resting paper. 1 regret that I cannot touch upon the observa- 

 tions which It contains respecting the alterations in the morals, 

 the habits, and the feelings of the common workmen produced 

 by, or accompanying these, improvements. They deserve the 

 particular attention of statesmen and political economists. 

 Unless means can be fallen upon to prevent that degeneracy 

 which has hitherto been the lot of all the manufacturing popu- 

 lation in every country, it is obvious that all manufacturing- 

 countries must sooner or later work their own destruction. The 

 following is the quantity of raw cotton consumed or converted 

 into yarn in Great Ihitain and Ireland durino- 1817 : 



o 



Total imported 1 10,000,000 lbs. 



Loss in spinning (l-^ oz. per lb.) 10,312,500 lbs. 



Yarn produced , 99,087,500 lbs. 



Number of hanks (at 40 per lb.) 3,987,500,000 



Number of spindles employed (each producing 



two hanks per day, and 300 working days in 



the year) ' 6,645,833 



Number of persons employed (supposing each 



to produce 120 hanks per day) . 1 10,763 



Number of horses power employed (supposing 



4-}r oz. coal to produce one hank of the 40 



and 180 lbs. coal per day = one horse power) 20,768 



IX. Memoirs on a new System of Cog and Toothed Wheels. 

 By Mr. James White, Engineer. — Mathematicians have demon- 

 strated that the form of the teeth of wheels, in order to move 

 equably and without fricnon, should be regulated by the curve 

 ealled the epicycloid. But this holds only when the pins of the 

 pinions which they put in motion are indefinitely small, which 

 never can hold in practice. This circumstance has prevented 

 workmen from attempting to make the figure of the teeth of 

 their wheels correspond with the theoretical figure. The object 

 of the present paper is to make known a method of cutting the 

 teeth of wheels so as that they shall give smooth and equable 

 motion, and as little friction as possible. For this method, a 

 patent was taken out some years ago by the author of the paper. 



X. On the I'leiibHity of all Mineral Substances, and the Cause 

 of Creeps and Scats in old Coal Mines. By Mr. John B. Long- 

 niire. — The author has observed a very great flexibility in sand- 

 stone and slate clay in excavated coal mines. He has likewise 

 seen certain varieties of limestone and clay-slate bend consider- 

 ably when in the act of being separated into small parts by 

 wedges and other tools. From thes?e facts, he infers that all 



