25 6 OBSERVATIONS 



that of the flill more oblique pair of mufcles reprefented in 

 the fame figure by the lines i D and i E. Let the mufcles 

 AD and AE be fuppofed to move the point A to number i, 

 and let the mufcles i D and iE be fuppofed to move number i 

 to number 2, or through a like fpace. It is evident, that in 

 the triangles i I E and 2 II E, the angles 1 I E and 2 II E are 

 equal; but as the angle 2 E II is larger than the angle 1 EI, 

 the angle II 2 E mufh be lefs than the angle I 1 E. Hence, as 

 the fides of triangles are longer in proportion to the width of 

 the oppofite angles, the fide I E will be longer in proportion 

 to 1 E, than the fide II E is in proportion to 2 E. The muf- 

 cular fibres, therefore, A D and A E, in bringing the point A 

 down to number 1, will lofe more, in proportion of their 

 length, than the more oblique fibres 1 D and 1 E will do in 

 moving number 1 to number 2. 



To prove this by calculation, let us fuppofe the mufcle to 

 be flill reprefented by the hypotenufe of a right angled tri- 

 angle, five inches in length, and capable of fhortening itfelf 

 one inch, and that one of the other fides meafures four inches, 

 and that the third fide meafures three inches. But let the fide 

 3 form the bafis of the triangle, and the fide 4 its perpendi- 

 cular, as in T. 2. fig. 7. 



In this cafe, the fquare of the hypotenufe, when it has 

 fhortened itfelf one inch, will be 16, from which deducting 9, 

 the fquare of the bafis, the number 7 remains for the fquare 

 of the perpendicular. But the fquare root of that number 

 being more than 2^, the oblique mufcles, fhortened one-fifth, 

 cannot bring the point A down 1^ inch, or to B, or cannot 

 move the point A half fo far as they were fhewn to do, when 

 the obliquity was greater, by making the bafis 4 inches and 

 the altitude 3 inches. 



Or let us, on the other hand, increafe the obliquity, as in 



T. 2. fig. 8. by fuppofing two right-angled triangles, fo con- 



2 ftrufted 



