PREPACEv IX 



%een discovered with respect to galvanic electricity ,• and I have for- 

 tunately been able to profit by Mr. Davy's most important experi- 

 ments, which have lately been communicated to the Royal Society, 

 and which have already given to this branch of science a much 

 greater perfection, and a far greater extent, than it before possessed. 

 The historical part of the work can scarcely be called new, but several 

 of the circumstances, Avhich are related, have escaped the notice of 

 former writers on the history of the sciences. 



Besides these improvements, if I may be allowed to give them that 

 name, there are others, perhaps of less importance, which may still be 

 interesting to those who are particularly engaged in those departments 

 of science, or of mechanical practice, to which they relate. Among these 

 may be ranked, in the division of mechanics, properly so called, a. 

 simple demonstration of the law of the force by which a body revolves 

 in an ellipsis ; another of the properties of cycloidal pendulums ; an 

 examination of the mechanism of animal motions ; a comparison of 

 the measures and weights of different countries ; and a convenient 

 -estimate of the effect of human labour : with respect to architecture, a 

 ^simple method of drawing the outline of a column : an investigation of 

 the best forms for arches ; a determination of the curve which affords 

 the greatest space for turning ; considerations on the structure of the 

 joints employed in carpentry, and on the firmness of wedges ; and an 

 easy mode of forming a kirb roof: for the purposes of machinery of 

 different kinds, an arrangement of bars for obtaining rectilinear mo- 

 tion ; an inquiry into the most eligible proportions of wheels and 

 pinions ; remarks on the friction of wheel work, and of balances ; a 

 mode of finding the form of a tooth for impelling a pallet without fric- 

 tion ; a chronometer for measuring minute portions of time ; a clock 

 «capement ; a calculation of the effect of temperature on steel springs; 

 an easy determination of the best line of draught for a carriage ; a« 

 VOL. I. b 



