194 On the Flow of Elastic Fluids through Orifices. 



theory, so far as respects those points of diiference between the 

 two theories specified in the first part of this article. 



The fifth column of the table shows the several differences be- 

 tween the experimental results, and those due to the new theory. 

 It will be noticed that these differences increase slightly between 

 density 10 and 13 in the receiver, before they begin to decrease. 

 This, I think, indicates a slight obstruction to the flow through ^ 



the second orifice, when the density in the receiver becomes equal 

 or nearly equal to that of the efiiuent stream. This increment at 

 its maximum amounts to '088, corresponding to the pressure of 

 that portion of an inch of mercury, and is, I think, the measure 

 of the obstruction or resistance due to that circumstance. If this 

 view of the subject is correct, then there would have been a de- 

 viation to this extent in this part of the table, even if the orifices 

 had been equal. 



It is desirable that further experiments of this kind should be 

 tried by those who have better means at command than I had to 

 do justice to the subject. To such as may be disposed to under- 

 take it, I would suggest that a perfect equality of the two orifi- 

 ces might be secured by interchanging the discs, varying the sizes 

 of the orifices until they gave the same indications in both posi- 

 tions. 



If, after thus securing the equality of the orifices, there should 

 still be a deviation in that part of the table where the elastic force 

 in the chamber is constant, such deviation. I think, must be at- 

 tributed to a change in the ratio of elastic force to density; and 

 if so, its amount would furnish the means of determining the law 

 according to which that ratio varies. 



1 would also suggest that a modification of this experiment 

 would furnish perhaps the best possible means of determining the 

 law according to which the ratio of elastic force to temperature 

 varies, when the absolute amount of heat is constant. In an ar- 

 rangement for this purpose, the bulb of a thermometer should be 

 inserted into the chamber; and the outer orifice should be so con- 

 structed that it maybe enlarged or diminished at pleasure. With 

 this arrangement, we may cause the air in the chamber to as- 

 sume, almost instantly, any elastic force we may choose, between 

 the elastic force of the atmosphere, and a little more than twice 

 the elastic force in the receiver; and we may keep that force 

 constant in the chamber dining any time that may be required to 

 cool the thermometer down to the corresponding temperature, the 

 continual flow through the chamber in the mean time carrying 

 off not only the heat which flows in from extraneous sources, 

 but also that derived from the thermometer itself. We may 

 thus ascertain the relation of elastic force to temperature at as 

 many points as we please within this range, and thereby deter- 

 mine the law of their variation when the absolute amount of 

 heat remains constant. 





