104- Prof. Oersted on the Compression of Gases. 



above the cylinder, the other distances having been measured, 

 by means of a separate scale. 



The tube Gil was lengthened for high pressures by our 

 joining together several tubes seven feet in length or more, by 

 means of iron screws. The experiment was always made in 

 the hall near the stairs of the house containing the cabinet of 

 natural philosophy of the university; there being no room 

 high enough for the lengthened tube GH. 



Several of the experiments we made, agreed in their results 

 with the Mariottic law: but a similar success did not attend 

 the whole of them, owing to the difficulty of making all the 

 cemented joints and screws resist the great pressure which 

 forces the mercury into them. 



In one experiment onhy, the results of which we shall com- 

 municate immediately, we were enabled to carry the pressure 

 to as many as eight atmospheres. The air contained in the 

 tube EF had been well dried by chloride of calcium ; the space 

 inside the tube, measured by mercury, amounted to 1054-8 

 grammes at 20° Cent. ; the pressure of the atmosphere on the 

 day of the experiment =0*7578 of a metre height of the mer- 

 cury. The following table shows the proportions which we 

 found between the compression of the air and the pressure of 

 the mercury. The first column contains the degrees of den- 

 sity of the original volume of air divided by the quantities of 

 space proportionally diminished by the compressing powers ; — 

 the second shows these powers in figures, assuming the pres- 

 sure of the atmosphere on the day of experiment as one; — the 

 third shows the differences between the different degrees of 

 density and compressing powers ; — and the fourth shows the 

 proportion borne by those differences to the compressing 

 powers. 

























Differences 







U3 



Differ. 



>> 



Com- 





divided by 



>, 



Com- 





divided 



■U 



pressing 



Differences. 



the com- 





pressing 



l4 



by 



S 



Powers. 





pressing 



a 



Powers. 



g 



compress 6 



Q 







Powers. 



Q 





Q 



Powers. 



1-000 



1-000 



•oooo 



•oooo 



3-168 



3-147 



+ 0-021 



+ 0-007 



1-1052 



1-1051 



+ 0-0001 



+ 0-0001 



3-616 3-599 



+ 0-017 



+ 0-005 



1-1676 



1-1693 



-0-0017 



-0-0015 



4-209 4-185 



+ 0-024 



+ 0-006 



1-2763 



1-2706 



+ 0-0030 



+ 0-0024 



5-057 



5-010 



+0-047 



+ 0-009 



1-4744 



1-4694 



+ 0-0050 



+ 0-0035 



5-603 5-572 



+ 0-031 



+ 0-005 



1-587 



1-581 



+ 0-006 



+ 0-004 



6-2886-287 



+ 0-001 



+ o-ooo 



1-812 



1-806 



+ 0-006 



+ 0-003 



7-7257-082 



+ 0-093 



+ 0-013 



2-112 



2-079 



+ 0-033 



+ 0-016 



8*030: 8-014 



+ 0-016 



+ 0-002 



2-529 



2-520 



+ 0-009 



+ 0-004 



1 







It 



