This series of observations and experiments will undoubtedly be received with uncommon regard by the inquisitive and speculative, being the product of two men, of whom one is eminent for mathematical learning, and the other for experimental curiosity, and both at once the favourites of those who cultivate the abstruser and politer arts. One has already published the Lectures on Respiration, and the other Electrical Experiments.2

They begin with great propriety, by laying down the doctrine which they undertake to prove.

Whether the existence of this aether, which is perhaps but the materia subtilis with a new name, is proved from the following experiments, may perhaps appear when we examine them, but if we consider it as it is now assumed on the authority of Newton, it seems contrived only for the sake of assigning a cause of gravitation, which may be as well considered, as the primary physical agent, as a property impressed by the creator without any previous influence of matter. For what is gained to philosophy by the super-induction of aether but the necessity of answering another question, What is the cause of the gradual condensation of aether? That repulsion from other matter by which aether must be thus condensed as much requires a cause as gravitation, and to create a matter so different from all other matter, as to gravitate only towards itself, is perhaps one of the arts of a philosopher unwilling to be silent when he has nothing to say. Surely the primum mobile with the cycles and epicycles afforded solutions with which importunity might be equally silenced and curiosity equally satisfied.4

The authors having thus supposed an aether proceed to other propositions, which are so precisely expressed that they can scarcelya be given with the same clearness in any words but their own. . . .5

Many experiments are mentioned, which seem to have been made with great exactness, and have been considered with uncommon subtilty of reasoning, but as the experiments are connected with each other, and the theory arising from them cannot be well understood without them, this treatise does not well admit of an abstract. The authors towards the conclusion have the following observations.6