138 Oil Elasticity. 



Fig. 2. The animal of its natural size, the belly upwards. 



Fig. 3. Under part of the head as seen in a strong light, 

 by means of whieh not only the outward but also the in- 

 ward direction of its members is discernible : thus we see 

 the roots of the antennae join together and communicate 

 with the two great canals aa, which carry the blood to all 

 the parts ; and I am persuaded the forceps join issue there 

 too; but the parts are too glandular to allow of this being 

 distinctly seen. 



Besides, upon the creature eating some mackrel liver, a 

 great quantity of blood was discharged from the under fis- 

 sures near the tips of these forceps a great number of times. 

 Meeting with a medium of nearly the same density as it- 

 self (/. e. the water), it diffuses itself in the form of a thick 

 smoke issuing from a furnace chimney when fresh fuel is 

 added : after which the forceps became so close that no 

 magnifier I could use upon him would enable me to see 

 them : yet this affords a presumption that they are each a 

 kind of proboscis. Some blood was discharged from the 

 mouth at the same time. 



Fig. 4, The eye of its natural size. 



Fig. 5. The same magnified. 



London, C15, Toolev-street, 

 20th June 180.5. 



XXII. On Elasticity. By Alexander Tilloch. yhi 

 Essay read hcfore the Askesian Society in the Session 

 1802-3. 



Xt is not my intention in the present paper to enter upon 

 any inquiry respecting the laws by which elasticity acts, as 

 they have often been investigated already, and are well 

 known to every one acquainted with the first elements of 

 mechanics. I mean merely to confine myself to a few 

 thoughts on the physical cause of elasticity, or that pro- 

 perty of bodies which enables them, after any external pres- 

 sure, to restore themselves to their former figure. 



The cause of elasticity has been proposed to be accounted 

 for in various ways. The Cartesians held that it was a ne- 

 cessary consequence of their materia suhtilis, or matter of 

 the second element, making an effort to pass through pores 

 too narrow for it. Thus, when a straight elastic body is 

 bent by any force, the pores become contracted on the con- 

 cave side, and, if they were before spherical, become for 

 instance elliptical, or of some other form j and the materia 



suhtilis, 



I 



