so Mr. J. H. Grindley. An Experimental Investigation of 



portant to know the circumstances under which adiabatic flow could 

 be experimentally obtained. 



Many experimental results have already been given by various 

 experimenters which indicate the laws governing the flow through 

 various types of orifices, and to some extent bear out the theoretical 

 conclusions on the subject, but so far as the author is aware, no 

 experiments have yet been made with saturated steam, showing results 

 which entirely agree with those deduced from theory by assuming 

 adiabatic flow, and hence arose the necessity of making experiments 

 with this object in view. 



It appears from the theory, that when the ratio (the lower to the 

 higher) of the two pressures causing the flow through the orifice is 

 diminished below a certain value, the upper pressiu-e being kept 

 constant, the rate of discharge of the steam should be constant. This 

 value of the pressure ratio depends entirely on the law of expansion 

 assumed to hold during the flow. By assuming this law to be repre- 

 sented by an equation of the form 



= constant, 



p being the pressure, v the specific volume of the gas, and n a constant 

 for any particular gas, we can deduce this value of the pressure ratio 

 giving maximum flow in the form 



l\ \n^\j 



Putting n = 10/9 we get for saturated steam expanding adiabati- 

 cally during its flow through the orifice. 



= 0-5824. 



If now the flow of steam be truly adiabatic in an experiment, this 

 particular value of the pressure ratio giving the maximum flow should 

 be actually found by the experiment, and if some other value than 

 this be obtained the law of flow will not then be the true adiabatic 

 one for saturated steam. 



Ilcnce the attainment of this particular value of the pressure ratio 

 giving the maximum discharge was made the object of the experi- 

 mental inquiry here described, since it would follow that the law of 

 expansion through the orifice was then truly the adiabatic law for 

 saturated steam. 



To begin with, an orifice was drilled in a piece of thin sheet brass 

 the nature of which should create, if possible, a large deviation from 

 the adiabatic in the actual law of flow through the orifice. Experi- 

 ments were then macie with this orifice placed between a steam chest 

 and a condenser, the weight of steam passing per minute being taken 



