9. Succeeding speculators in his school attempted to follow out this view. Dr. Frend, of Christ Church, in 1710, published his _Prælectiones Chymicæ, in quibus omne fere Operationes Chymicæ ad vera Principia ex ipsius Naturæ Legibus rediguntur. Oxonii habitæ_. This book is dedicated to Newton, and in the dedication, the promise of advantage to chemistry from the influence of the Newtonian discoveries is spoken of somewhat largely,--much more largely, indeed, than has yet been justified by the sequel. After declaring in strong terms that the only prospect of improving science consists in following the footsteps of Newton, the author adds, 'That force of attraction, of which you first so successfully traced the influence in the heavenly bodies, operates in the most minute corpuscles, as you long ago hinted in your _Principia_, and have lately plainly shown in your _Opticks_; and this force we are only just beginning to perceive and to study. Under these circumstances I have been desirous of trying what is the result of this view in chemistry.' The work opens formally enough, with a statement of general mechanical principles, of which the most peculiar are these:--'That there exists an attractive force by which particles when at very small distances from each other, are drawn together;--that this force is different, according to the different figure and density of the particles;--that the force may be greater on one side of a particle than on the other;--that the force by which particles cohere together arises from attraction, and is variously modified according to the quantity of contacts.' But these principles are not {12} applied in any definite manner to the explanation of specific phenomena. He attempts, indeed, the question of special solvents[10\6]. Why does _aqua fortis_ dissolve silver and not gold, while _aqua regia_ dissolves gold and not silver? which, he says, is the most difficult question in chemistry, and which is certainly a fundamental question in the formation of chemical theory. He solves it by certain assumptions respecting the forces of attraction of the particles, and also the diameter of the particles of the acids and the pores of the metals, all which suppositions are gratuitous. [Note 10\6: P. 54.]