320 Review of Prof. Johnson’s Report on American Coals. 
Forty three similar tables contain the deductions relative to 
the various kinds of fuel assayed. Many very important facts 
are recorded in the tables of daily observations, applicable to the 
elucidation of questions indirectly involved in these experiments. 
Those relating to the expansion of water above 212° are particu- 
larly deserving of notice for the relation they bear to the causes 
of steam boiler explosions. The greatest care seems to have been 
taken to make the observations on this subject correct, as it was 
important to be able to determine the volume of the water at any 
given temperature that would correspond with the same quantity 
at the normal temperature, and to assure the observers that the 
boiler contained the same weight of water at the beginning and 
end of an experiment. 
These observations thus made, merely for the correcting of 
those on the weight of water supplied, and not under the influence 
of any theoretical views, are scarcely systematic enough for the 
establishment of a general law, but they lead strongly to the in- 
ference that a general law does exist for the expansion of water 
above 212°, and that the ratio of that expansion increases with a 
rapidity not generally suspected. It is a subject preéminently 
worthy of more careful investigation; and its importance in a 
practical point of view is not diminished by the fact that a part of 
the apparent dilatation is due to the constant admixture of steam, 
throughout the mass of water, while in ebullition. Assuming the 
general fact to be true, that water under high temperatures and 
pressures does expand in a rapidly increasing ratio, we have the 
means of solving some of the most serious difficulties attending 
the explanation of the causes of many disastrous steam boiler ex- 
plosions, and particularly those of the high pressure character, on 
our western waters. The following note from page 13 of the 
Report, will give a condensed view of the facts collected on the 
subject of expansion of water by heat. 
“The observations made on the gradual rise of temperature, 
and the correspondent weights of water which it took to fill the © 
boiler, as much as the expansion by heat did, gave the following 
table., The weight of water operated on was 12,795 lbs. 
From 66° to 1144°, viz. 48°°5, the increase = bulk of 69 Ibs. at 589, or 1:42 Ibs. to 1° 
1143 to 149 Si gy fetisy, sc s 81 * or 2:35 “ tol 
149 to 180 Lay se Be Syl oe or 3:13 “ tol 
180 to 207 SL NOG Bb it Bons or 3:18 “ tol 
207 to 223 tie 16 AG 4 89. or 5:56 “ tol 
223 to280 #7 oi soli se orl014 “ tol 
