466 I'HILOSOPHICAL TRANSACTIONS. [aNNO 1795. 



intended to establish the facts themselves, in doing which I have already taken 

 up too much of the time of the r. s., I shall at some future period consider 

 their application to the phenomena of vision in health and disease. 



Fig. 10, pi. 5, shows portions of the four straight muscles of the eye, with 

 their tendons insensibly lost in the external lamina of the cornea, stretched out 

 and dried. The tendons become broader as they approach the cornea, and form 

 a circle of which the cornea appears to be a continuation. 



//. The Bakerian Lecture. Being Observaliotis on the Theory of the Motion 

 and Resistance of Fluids ; ivith a Description of the Construction of Experi- 

 ments, in order to obtain some Fundamental Principles. By the Rev. Samuel 

 Vince, AM., F.R.S. p. 24. 



However satisfactory the general principles of motion may be, when applied 

 to the action of bodies on each other, in all those circumstances which are 

 usually included in that branch of natural philosophy called mechanics, yet the 

 application of the same principles in the investigation of the motions of fluids, 

 and their actions on other bodies, is subject to great uncertainty. That the dif- 

 ferent kinds of airs are constituted of particles endued with repulsive powers, is 

 manifest from their expansion when the force with which they are compressed is 

 removed. The particles being kept at a distance by their mutual repulsion, it is 

 easy to conceive that they may move very freely among each other, and that this 

 motion may take place in all directions, each particle exerting its repulsive power 

 equally on all sides. Thus far we are acquainted with the constitution of these 

 fluids ; but with what absolute degree of facility the particles move, and how 

 this may be effected under different degrees of compression, are circumstances 

 of which we are totally ignorant. 



In respect to those fluids which are denominated liquids, we are still less ac- 

 quainted with their nature. If we suppose their particles to be in contact, it is 

 extremely difficult to conceive how they can move among each other, with 

 such extreme facility, and produce effects in directions opposite to the impressed 

 force without any sensible loss of motion. To account for this, the particles 

 are supposed to be perfectly smooth and spherical. If we were to admit this 

 supposition, it would yet remain to be proved how this would solve all the phe- 

 nomena, for it is by no means self-evident that it would. If the particles be not 

 in contact, they must be kept at a distance by some repulsive power. But it is 

 manifest that these particles attract each other, from the drops of all perfect 

 liquids affecting to form themselves into spheres. We must therefore admit in 

 this case both powers, and that where one power ends the other begins, agree- 

 able to Sir Isaac Newton's* idea of what takes place, not only in respect to the 

 constituent particles of bodies, but to the bodies themselves. The incompressi- 



* See his Optics^ Que. 31.— Orig. 



