sic*. ii.} DISSERTATION SECOND. 85 



a just idea of their utility in general, he was unacquainted 

 with roost of them. The most remarkable at present are 

 those that follow : 



1. Agronomical instruments, or, more generally, all in- 

 struments for measuring lines and angles. 



2. Instruments for measuring weight or force ; such are 

 the common balance, the hydrostatick balance, the baro- 

 meter, the instruments used in England by Cavendish, and 

 in France by Coulomb, which measure small and almost in- 

 sensible actions by the force of torsion. 



These last rather belong to the class of the instantiae 

 luctae, where force is applied as the measure of force, than 

 to the instantiae radii. 



3. The thermometer, newly invented in the time of 

 Bacon, and mentioned by him under the name of Vitrum 

 Calendare, an instrument to which we owe nearly all the 

 knowledge we have of one of the most powerful agents in 

 nature, viz. Heat. * 



4. The hygrometer, an instrument for measuring the 

 quantity of humidity contained in the air ; and in the con- 

 struction of which, after repeated failures by the most 

 skilful experimenters, the invention of Professor Leslie now 

 promises success. Almost every one of these instruments, 

 to which several more might be added, has brought in sight 

 a new country, and has enriched science not only with new 

 facts, but with new principles. 



Among the remarks of Bacon on the experimenta radii, 

 some are very remarkable for the extent of view which 

 they display even in the infancy of physical science. He 

 mentions the forces by which bodies act on one another at 

 a distance, and throws out some hints at the attraction 

 which the heavenly bodies exert on one another. 



" Inquirendum est," says he, " si sit vis aliqua magneti- 

 ca quae operetur per consensum inter globum terrae et 



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