818 
PROFESSOR O. REYNOLDS ON CERTAIN DIMENSIONAL 
b'y for the difference of pressure on the two sides of the plate. 
dr . 
b ~ for the difference of temperature on the two sides of the plate. 
The suffix s will be used to distinguish quantities relating to the stucco plate, and 
m to distinguish those relating to meerschaum. 
x y are the coordinates of a point on any one of the curves on fig. 8, Art. 40, or 
Plate 48, which are the logarithmic homologues of the experimental curves. 
105. The experimental result I. follows from the general form of equation (101). 
cIt 
For putting, as in the experiment on transpiration under pressure, — = 0 and M 
and - t- constant, equation (101) becomes 
JO CtX 
/£;i 
( 102 ) 
The times of transpiration are proportional to — for the same tube or plate, and if 
V be a factor depending on the number and size of the openings through the plate, 
we have the time of transpiration equal to 
Putting 
2/ =1 °g 7i’ - T = lr, g \ 
(103) 
And indicating the quantities referring to particular plates by s and m, we have 
c 
as,+log c,=log j | 
Cm < 
x m +\og c„=log - 
Sy/i 
(104) 
Whence taking the coefficients A, m, A la \. 2 , to be the same for stucco as for meer- 
c c 
schaum (see Appendix, note 4), it follows from equation (102) that when - = — 
s$ s m 
X s =X m -\-\og 
and 
y s =y„- log 
m J 
s I 
(105) 
Hence we see that the curves expressing the relation between the logarithms of the 
reciprocals of the mean ranges and the logarithms of the times of transpiration 
must have the same shape for different plates, such as stucco and meerschaum. And, 
