Its fundamental postulate, at any rate, has been curiously verified in the course of recent researches into the arcana of physics. Entities in some degree corresponding to the ultramundane corpuscles of the Genevese philosopher do actually exist. Electrons are being continually expelled from bodies in all parts of the universe; they issue forth under all conceivable conditions and in unlimited numbers. Space is perhaps thronged with them; no material object can be exempt from their multitudinous buffetings, which are beginning to be taken account of in many cosmical speculations, and cannot certainly be ignored in efforts to solve the most obvious to superficial apprehension, the most intricate on a profound consideration, of all cosmical problems. But there is one fatal objection to an electronic theory of gravitation. The agency appealed to travels too slowly to be available for the required purpose. The velocity of light, there is reason to believe, sets a limit impossible to be surpassed or even attained by the velocity of electrons; yet it is incomparably smaller than the rate of gravitational transmission. Tisserand estimated at six million times the quickness of luminous travel the minimum speed at which the sun's attraction must be propagated in view of the imperceptibility in planetary observations of effects corresponding to a time-inequality;[67] and this value may be taken as authentic. So colossal a discrepancy excludes any kind of impact-rationale of the mutual pull of heavy masses; Lesage's corpuscles remain 'ultramundane'; their identification with known atoms or sub-atoms appears to be precluded; no products of ionic disintegration possess the qualities necessarily to be ascribed to them.