156 ON MR. EWART’S PAPER, ETC. 
Moseley has sought for this relation in different 
machines, giving to it the name of the ‘“‘ modulus” 
of the machine. 
In every machine the velocity of the different 
parts is connected by certain invariable relations, 
capable of being expressed mathematically, and 
these relations have been determined, in many 
instances of complex machinery, in the valuable 
work of Professor Willis, entitled ‘“‘'The Princi- 
ples of Mechanism.” 
In closing this notice of Mr. Ewart’s principal 
scientific effort, I feel desirous of bearing my 
testimony to the purity and disinterestedness of 
his love for science, particularly that which had a 
direct practical application; and to mention that 
whatever estimation may be given to my own 
humble experimental efforts, it is probable that 
none but the earliest of them would ever have 
been made had it not been for the encouragement 
given by Mr. Ewart, who first introduced me to 
my liberal friend Mr. Fairbairn, and afterwards 
was present through the whole series of my ex- 
periments on the strength and best forms of iron 
beams, the results of which were published in the 
fifth volume of the memoirs of this society. 
