342 COSMOS. 



1600, under the title of " Physiology of Magnets and of the 

 Earth as a great Magnet (de magno magnete tellure)." *' The 

 property," says Gilbert, " of attracting light substances, when 

 rubbed, be their nature what it may, is not peculiar to amber, 

 wliich is a condensed earthy juice cast up by the waves of 

 the sen, and in which flying insects, ants, and worms lie en- 

 tombed as in eternal sepulchers (aeternis sepulchris). The 

 force of attraction belongs to a whole class of very different 

 substances, as glass, sulphur, sealing wax, and all resinous sub- 

 stances, rock crystal, and all precious stones, alum, and rock 

 salt." Gilbert measured the strength of the excited electrici- 

 ty by means of a small needle, not made of iron, which moved 

 freely on a pivot {versorium electricmn), and perfectly similar 

 to the apparatus used by Haiiy and Brewster in testing the 

 electricity excited in minerals by heat and friction. "Fric- 

 tion," says Gilbert further, " is productive of a stronger ef- 

 fect in dry than in humid air; and rubbing with silk cloths 

 is most advantageous. The globe is held together as by an 

 electric force (?) Globus telluris per se electrice congregatur 

 et cohaeret ; for the tendency of the electric action is to pro- 

 duce the cohesive accumulation of matter (motus electricus 

 est motus coacervationis materise)." In these obscure ax- 

 ioms we trace the recognition o£ terrestrial electricity — the ex- 

 pression of a force — which, like magnetism, appertains as 

 such to matter. As yet we meet with no allusions to re- 

 pulsion, or the diiference between insulators and conductors. 

 Otto von Guericke, the ingenious inventor of the air pump, 

 was the first who observed any thing more than mere phenom- 

 ena of attraction. In his experiments with a rubbed piece 

 of sulphur, he recognized the phenomena of repulsion, which 



nostris motionibus coi-pora allicere videntur, Electrica et Magnetica ; 

 Electrica naturalibus ab humore effluviis ; Magnetica formalibus effi- 

 cientiis seu potius pi'imariis vigoribus, incitationes faciunt. Facile est 

 horainibus ingenio acutis, absque experimentis et usu rerum labi, et 

 errare. Substantia? proprietates aut familiaritates, sunt generales ni- 

 mis, nee tamen ver^e designataj causse, atque, ut ita dicam, verba quce- 

 dam sonant, re ipsa nihil in specie ostendunt. Neqjie ista succini cre- 

 dita attractio, a singular! aliquaproprietate substantia?, aut familiarita- 

 te assurgit ; cum in pluribus aliis corporibus eundern elfectum, majori 

 industria invenimus, et omnia etiam coi*pora cujusmodicunque proprie- 

 tatis, ab omnibus illiis alliciuntur." (Z>e Magnete, p. 50, 51, 60, and 

 65.) Gilbert's principal labors appear to fall between the years from 

 1590 to 1600. Whewell justly assigns him an important place among 

 those whom he terms "practical reformers of the physical sciences." 

 Gilbert was surgeon to Queen Elizabeth and James I., and died in 

 1603. After his death there appeared a second work, entitled "Z>e 

 Mundo nostra Suhlunari IViilosophia Nova." 



