342 Mr. smeaton’s Fundamental Experiments 
ibftiiefs, at the fame time that their elaftic fp rings, fo far as they 
reach, are very ftiff; and hence we may (by the way) con- 
clude, that the fame, mechanic power that is required to 
change the figure in a final l degree of thofe bodies that have the 
popular appellation of hard bodies, would change it in a great 
degree in thofe bodies that approach towards foftnefs, by hav- 
ing a iinall degree of tenacity or cohefion. In the former 
kind we may rank the harder kinds of caji iron , and in the 
latter, foft tempered clay. 
While the philofophical world was divided by the difpute 
about the old and new opinion , as it was called, concerning the 
powers of bodies in motion, in proportion to their different veloci- 
ties : thofe who held the old opinion contending, that it was as 
the velocity j imply , afked thofe of the new, How, upon then- 
principles, they would get rid of the conclulions arifing from 
the doctrine of. unelaftic perfectly hard bodies? They replied. 
They found no fuch bodies in nature, and therefore did not 
concern thcmfelves about them. On the other hand, thofe of 
the new opinion alked thofe of the old, How they would 
account for the cafe of non-elaftic foft bodies, where, accord- 
ing to them, the whole motion loft by the ftnking body was 
retained in the two after the ftroke (the two bodies moving 
together with the half velocity), though the two non- 
eiaftic bodies had been bruifed and changed their figure by the 
ftroke ; for, if no motion was loft, the change of figure 
muft be an effect without a caufe ? To obviate this, thofe of 
the old opinion ferioufly fet about proving, that the bodies 
might change their figure, without any lofs of motion in either 
of the ftriking bodies. 
Neither of thefe anfwers have appeared to me fatisfaffory, 
efpecially fince my mill experiments : for with refpedt to the 
firft, it is no proper argument to urge the impoflibility of find- 
