18 PHILOSOPHICAL TRANSACTIONS. [aNNO 1744. 



lated blood. There was also found a quantity of blood, partly florid, partly dark, 

 coloured and coagulated, in a portion of the jejunum, as well as in the ileum, 

 colon, and rectum, in which last the blood was in a very putrid state. 



On the Jclion of Springs. By James Jurin, M. D.. F. R. S. N° 472, p. 46. 



The theory of springs is not only of use in the more curious parts of mechanics, 

 as the structure of watches, &c. but may give light to many operations of nature, 

 there being few substances but what are endued with some degree of elasticity; 

 and particularly the bodies of animals, and even of vegetables, being known to 

 consist, in a great measure, if not wholly, of organs strongly elastic. 



For which reason it is not to be wondered, that this theory has engaged the 

 thoughts of several eminent mathematicians of the last and present age; as Dr. 

 Hook, Mr. John Bemouilli, M. Camus, &c. 



But, as all hitherto done on this subject goes no further, than to compare the 

 effects of different springs with each other, in one case only, where they are sup- 

 posed to be bent to the same degree, and that without showing how the effect of 

 any of them may be reduced to, or compared with, that of any other natural 

 cause, the general proposition following may merit attention, both on account of 

 its simplicity, and of its comprehending all possible cases of a body acting on a 

 spring, or a spring on a body, where no other power intervenes; and also of its 

 reducing the effect to that most known and simple one, the effect of gravity on 

 falling bodies. 



1. By a spring is meant a body of any shape perfectly elastic. — 1. By the na- 

 tural situation of a spring, is meant the situation it will rest in, when not dis- 

 turbed by any external force. — 3. By the length of a spring, is meant the greatest 

 length, through which it can be forced inwards. This would be the whole length, 

 were the spring considered as a mathematical line; but in a material spring is 

 the difference between the whole length when the spring is in its natural situa- 

 tion, and the length or space it takes up when wholly compressed or closed. — 

 4. By the strength of a spring, is meant the least force or weight, which, when 

 the spring is wholly compressed or closed, will restrain it from unbending itself. 

 — 5. By the space through which a spring is bent, is meant that space or length 

 through which one end of the spring is removed from its natural situation. — 6. 

 By the force of a spring bent or partly closed, is meant the least force or weight, 

 which, when the spring is bent through any space less than its whole length, 

 will confine it to the state it is then in, without suffering it to unbend any 

 farther. 



Principle. — Ut tensio, sic vis: that is, if a spring be forced or bent inwards, 

 or drawn outwards, or anywise removed from its natural situation, its resistance 

 is proportional to the space by which it is removed from that situation. 



