known to the ancients at all (which may reasonably 

 be doubted) yfet the art \vas wholly lost for many ages, 

 and not recovered till of late years. 



18. Later ages have likewise made many discoveries 

 with regard to earth, water, fire, and air : the last of 

 which, air, though it be of so fine a texture as to be 

 wholly invisible, yet producing such amazing effects, 

 has excited the most diligent enquiries of the curious. 

 Tslor does any part of philosophy afford a wider field 

 for experiments and discoveries. The weight of it we 

 can ascertain by that curious instrument the barometer, 

 invented by Torricellius; the degrees of toat and cold 

 by the thermometer. By the air-pump (invented by 

 Otto Guerick, Mayor of Magdeburg h) the air is drawn 

 out of any bodies, or more largely thrown into them, 

 and hereby many effects are produced which deserve 

 our diligent consideration. 



19. With regard to water, the discoveries of later 

 times are numerous and important. Such are the 

 diving-bell, invented by George Sinclair : the diving- 

 machine of Alphonso Borelli, a kind of boat which is 

 so contrived as to be navigated under water : and th 

 art of making salt-water fresh, which is now done with 

 li( tie expence, so far that the saltuess is taken away, 

 and it is fit for almost all uses. 



20. The nature and properties of fire also have been 

 accurately traced in late ages : for which new occasion 

 was given by the invention of gunpowder, by Berfhold 

 Schwartz, in the fourteenth century. Aurum Fulmi- 

 nans, a yet later invention, goes oti* with a louder ex- 

 plosion than gunpowder. Other bodies there are, 

 which do not burn, yet emit light ; such is the Bo- 

 nouian stone, which placed in the dark, diffuses light 

 like a burning coal. It is well known that the prepa- 

 ration called phosphorus* has the same property. 



21. Various theories of the earth have lately appear- 

 ed, but they are no more that* ingenious conjectures. 

 The same may be said of the systems of the Universe, 

 a lew particulars exeepted. The Ptolemaic system, 

 \vhjch supposes th<; earth to be the centre of the Uni* 



