C H D 
II. The Bakerian Lecture. Observations on the Theory of the 
Motion and Resistance of Fluids ; with a Description of the 
Construction of Experiments , in order to obtain some funda- 
mental Principles. By the Rev. Samuel Vince, A. M. F.R. S. 
Read November 27, 1794. 
ITowever satisfactory the general principles of motion may 
be, when applied to the action of bodies upon 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 upon other bodies, is subject to great 
uncertainty. That the different 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 amongst 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 affected 
under different degrees of compression, are circumstances of 
which we are totally ignorant. In respect to those fluids 
whiph are denominated liquids, we are still less acquainted 
