THE FORCE OF GRAVITATION 



IS 



this marble and change it in the same manner as I can 

 change ice into water and water into steam. I can convert 

 a part of it into its own steam easily, and show you that 

 this steam from the marble has the property of remaining 

 in the same place at common temperatures, which water- 

 steam has not. If I add a little liquid to the marble and 

 decompose it ('), I get that which you see [the lecturer here 

 put several lumps of marble into a glass jar, and poured 

 water and then acid over them; the carbonic acid immedi- 

 ately commenced to escape with considerable effervescence] 

 the appearance of boiling, which is only the separation of 

 one part of the marble from another. Now this [marble] 

 steam, and that [water] steam, and all other steams, gravitate 

 just like any other substance does; they all are attracted 

 the one toward the other, and all fall toward the earth, and 

 what I want you to see is that this steam gravitates. I have 

 here (Fie. 2) a large vessel placed upon a balance, and the 



FIG. 2 



moment I pour this steam into it you see that the steam 

 gravitates. Just watch the index, and see whether it tilts 

 over or not. [The lecturer here poured the carbonic acid 

 out of the glass in which it was being generated into the 

 vessel suspended on the balance, when the gravitation of the 

 carbonic acid was at once apparent.] Look how it is going 



Add a little liquid to the marble and decompose it. Marble is composed 

 of carbonic acid and lime, and, in chemical language, is called carbonate 

 of lime. When sulphuric acid is added to it, the carbonic acid is set free, 

 and the sulphuric acid unites with the lime to form sulphate of lime. 



Carbonic acid, under ordinary circumstances, is a colorless invisible gas, 

 about half as heavy again as air. Dr. Faraday first showed that under 

 great pressure it could be obtained in a liquid state. Thilorier, a French 

 chemist, afterward found that it could be solidified. 



