VI PREFACE. 



A slight sketch of the papers comprised in this volume may 

 not be uninteresting. 



The first paper, which is also the longest and perhaps the 

 most important, was published by subscription at Nottingham 

 in 1828. It was in this paper that the term potential was first 

 introduced to denote the result obtained by adding together 

 the masses of all the particles of a system, each divided by its 

 distance from a given point. In this essay, which is divided 

 into three parts, the properties of this function are first con- 

 sidered, and they are then applied, in the second and third 

 parts, to the theories of magnetism and electricity respectively. 

 The full analysis of this essay which the author has given in 

 his Preface, renders any detailed description in this place un- 

 necessary. In connexion with this essay, the corresponding 

 portions of Thomson and Tait's Natural Philosophy should 

 be studied, especially Appendix A. to Chap. I., and Arts. 482 

 550, inclusive. 



The next paper, " On the Laws of the Equilibrium of Fluids 

 analogous to the Electric Fluid,'* was laid before the Cambridge 

 Philosophical Society by Sir Edward Ffrench Bromhead, in 

 1832. The law of repulsion of the particles of the supposed 

 fluid here considered is taken to be inversely proportional to 

 the n ih power of the distance. This paper, though displaying 

 great analytical power, is perhaps rather curious than practically 

 interesting ; and a similar remark applies to that which succeeds 

 it, "On the determination of the attractions of Ellipsoids of 

 variable Densities," which, like its predecessor, was communi- 

 cated to the Cambridge Philosophical Society by Sir E. F. 

 Bromhead. Space of n dimensions is here considered, and 

 the surfaces of the attracting bodies are supposed to be repre- 



