Un the Production of Steam from heated Iron. 75 
almost exactly coincident with an arithmetical progression. Thus the 
12th series, from the 11th to the 20th experiment, inclusive, may 
be regarded as composed of the numbers 8, 9, 10, FL, 12,.13; 14, 
15, 16, 17, while from the 23rd to the 28th, we have 26, 30, 36, 
44, 59, 89, yielding the ratios 32=1/153, 3&=1.200, 44=1.222, 
+7=1.341, and 221.508, and the mean of all these ratios is 1.285. 
By similar operations applied to the concluding part of every series 
in this course except the first and second, we obtain the following 
mean ratios for the several series respectively, viz. 
for the 3rd series 1.290 * 
soe eet? “-aaeoe 
as ee cage co 
oe Se kee. coe 
If we would know the mean of all their mean ratios, we have but 
to divide their sum by 10, the number of series considered, whence 
we obtain 1.296 for the general ratio of this part of the several se- 
nes. It will, however be remarked that the five ratios belonging to 
the 11th series are themselves in geometrical progression, whose 
mean ratio is 1.07, 
order to present to the eye the whole range of experiments in 
some of the series, I have adopted the method of curvilinear projec- 
tion, assuming as the unit of vapor, the amount actually employed at 
each trial, and as the unit of time, the number of seconds taken to 
“aporize it, at the period of most rapid action. Representing these 
units by equal vertical and horizontal lines respectively, the relative 
time of action in each experiment marked on the line ac, is denoted 
by the dotted lines, ad, cg, &c. Figs. 1,2 and3. Regarding ab 
4S @ Constant quantity, we have the portions of time above the mini- 
mum, represented by that part of each vertical which is above the 
sent bf. Tt will be seen by Fig. 1. that the arithmetical series 
sea the 6th, 7th, and sth experiments. Fig. 2d. shows the 
Neidio ge at the 17th 18th, and 19th, while the 12th series, rep- 
sista y Fig. 3, shows a straight line from No. 11, to No. 20, as 
*ady stated. See the plate at p. 71. 
