48 REPORT—1858. 
vance of human enterprise, travel, and observation. The epochs of printing 
and the Reformation are those of the first great expansion, while the dis- 
covery of the new world, the voyage to India round the Cape, and the vast 
accessions of European colonization and commerce of the last 150 years, 
connect themselves as causes with the two latest curves. We have traced 
at once the history of a physical law and that of human progress. How far, 
then, is it possible to disentangle these elements, so as to arrive at a con- 
clusion as to whether seismic energy over the world is progressive, constant, 
or retrogressive? To do so perfectly is perhaps impossible; the elements 
by which the rate of observational knowledge has been determined are too 
complex and too imperfectly known to render any attempt to fix its rate of 
expansion in time probable. Even the area of observation itself, the land 
and water known to history at given epochs, can be but vaguely sketched ; 
as vaguely also the number of observers, and the determination of the human 
mind towards observation. (See Appendix I.) 
This much is certain, however ;—that up to, and even beyond the Christian 
era, no record of earthquakes exists for any portions of the earth’s surface, 
except for limited areas of Europe and Asia, and a still more restricted 
patch of Northern Africa, and, if Kaempfer, is to be credited, for Japan, of 
which, however, we know nothing for certain. Yet, of the enormously 
larger areas of the then outer and unknown world since discovered, it is not 
to be supposed but that there was a proportionate (perhaps even for the 
“New World” a more than proportionate) amount of earthquake energy, 
though not recorded cr even known to mankind. 
If, however, the curve of total energy (Plate VII.), in which the facts of 
all the preceding are condensed into a single line, be examined and com- 
pared by a broad glance with the great outlines of human progress, the con- 
clusion appears sufficiently warranted, that during all historic time the amount 
of seismic energy over the observed portions of our world must have been 
nearly constant. To assume that earthquake disturbance has been con- 
tinually on the increase, would be to contradict all the analogies of the 
physics of our globe. These analogies might lead us to suppose that, like 
other violent presumed periodical actions, they were getting spent, and that 
the series of earthquake shocks would be found a converging one. Were 
this so, however, to any considerable extent, we should not find the vast 
expansions of results which the last 300 years present; or, although the ex- 
pansion might be absolutely large, its divergence would not present such 
decisive features of progressive increase. The results due to the number of 
observers would be more or less balanced by the increasing paucity of events 
to observe and record; but this appears conclusively to lead to the deduc- 
tion we have made, namely, that if the curve of total energy be closely 
examined century by century, it will be found that, at periods of social torpor 
and stagnation of observational energy (and this is so even far down the 
stream of time), the number of earthquakes remains nearly constant, or with 
a very slight but nearly uniform increase. Thus, from the eleventh to the 
beginning of the fifteenth century, the abscissz are almost equal, the crests of 
the curves being nearly all ascribable to single great earthquakes, which made 
themselves felt over vast, areas. Their expansion just keeps pace, so far as can 
be judged, with that of contemporaneous human progress ; but if the series” 
was really a distinctly converging one, at such periods we should find the 
abscisse decreasing also. On the other hand, we find the increase in the — 
number of recorded earthquakes always coinciding with the epochs of in- 
creased impulse and energy in the march of the human mind. 
We therefore conclude that our evidence, such as it is, indicates a general 
