244. PROF. EDWARD HULL, ON THE ABNORMAL CONDITIONS 
tician; but those who have dipped, however slightly, into the 
Principia, will find that the demonstration was not a very simple 
matter. 
But it is the abnormal conditions of phenomena that more 
especially attract attention, and call for explanation, and I 
propose in the following paper to deal with two conditions of 
water which appear to be quite abnormal. These effects are of 
transcendent importance, and influence the harmonious working 
of the physical agencies around us; and yet have scarcely been 
recognized as being very different from what are regarded as 
the ordinary or normal results which we are acquainted with 
when we see that water flows down an inclined plane; or that 
when boiling it gives off steam. There are, indeed, many remark- 
able effects produced by water which I should like to have 
dealt with did time permit, such as its presence in the quartz 
of granite, and its solvent action on minerals when at high 
temperature and pressure, whereby these substances have been 
introduced into mineral veins. But I pass on to the subject more 
immediately before us, namely, the abnormal conditions under 
which waters occur ; and by “abnormal” I mean differing from 
those which we should be led to expect by comparison with 
other natural objects ; these conditions resolve themselves under 
two heads :— 
(1) The temperature of water at its maximum density of 
39°2° Fahr. (4° Cent.), and 
(2) Its incompressibility by which it probably differs 
from all other substances. 
The consequences of these abnormal conditions in the 
economy of nature are inestimable, and we shall consider them 
in the above order. 
(1) Maximum Density.—When water is at a temperature of 
212° F. under normal pressure it passes into steam and has a 
minimum density. Cooling down from this point it contracts or 
becomes denser as it grows cooler, until it reaches a tempera- 
ture of 39°2° Fahr. (4° Cent.) where the contraction is arrested ; 
and from this point down to 32° F. (that of freezing) it expands, 
producing ice, which being lighter than water, floats on its 
surface. Here it is, therefore, that the abnormal conditions 
arise, for the condensation might have been supposed to have 
continued throughout the intermediate seven degrees (from 392° 
to 32° F.) resulting in the formation of ice heavier than water, 
and consequently sinking down to the bottom of the basin or 
reservoir. Such, however, we know not to be the case, as eleven 
