206 



FERGUSON'S LECTURES. 



The air- 



pump,, let the air run into it through the flame of the oil 

 of turpentine ; then remove the cover of the receiver, 

 and holding a candle to that air, it will take fire, and 

 burn quicker or slower, according to the density of the 

 oleaginous vapour. 



When such combustible matter, as is above-mention- 

 ed, kindles in the bowels of the earth, where there is 

 little or no vent, it produces earthquakes, and violent 

 storms or hurricanes of wind when it breaks forth into 

 the air. 



An artificial earthquake may be made thus. Take 10 

 or 15 pounds of sulphur, and as much of the filings of 

 iron, and knead them with common water into the con- 

 sistence of a paste : this being buried in the ground, 

 will, in 8 or 10 hours' time, burst out in flames, and 

 cause the earth to tremble all round to a considerable 

 distance. 



From this experiment we have a very natural account 

 of the fires of mount Mtna, Vesuvius, and other volcanos, 

 they being probably set on fire at first by the mixture 

 of such metalline and sulphureous particles. 58 



The air-pump being constructed the same way as the 

 water-pump, whoever understands the one, will be at no 

 loss to understand the other. 69 



Having put a wet leather on the plate L L of the air- 



Note 58. Although the Editor has considered it adviseable to insert 

 the paragraphs entitled Fermentation, Thunder, Lightning, and Earth- 

 quakes, he yet feels it his duty to say, that they are, in most particu- 

 lars, inconsistent with sound philosophy. Our Author's Treatise ou 

 Electricity, adapted to the present state of science, is nearly ready for 

 publication. 



Note 69. \Ve are indebted for the invention of the air-pump to a 

 learned German, no less distinguished for his pneumatic knowledge, 

 than general scientific attainments : and though the memory of Otto 

 Guericke will be long remembered with gratitude and veneration, by 

 every lover of science, we must still bear in mind, that it was our coun- 

 tryman Boyle who converted it to real use. In the hands of Otto 

 Guericke it was an amusing toy, and a mere mechanical instrument: 

 in those of Boyle it became a truly philosophical machine. 



