46 Poe ee ee. REPORT—1858. 
and Philippine Island groups, including Luzon, incomparably the most im- 
portant and interesting earthquake region on the face of the earth, Berg- 
haus’s maps, 3 Abtheil. Geol. No. 8 und 10, “ Specialia vom Vulkan Giirtel,” 
&c., are worthy of all commendation, save as respects the outline of seismic 
regions already adverted to, and here repeated even in a more distorted 
form. 
Such have been the results of previous labours as to the distribution in 
time and space of earthquakes. I proceed to those deduced from our own 
researches. 
At the conclusion of the Second Report (1851), the principles upon 
which the British Association Earthquake Catalogue itself was compiled have 
been described ; it remains now to describe the methods by which it has 
been discussed, and to state the results. 
The collection of an earthquake catalogue is a work essentially of a sta- 
tistic character, and partakes of all that disadvantage and incompleteness 
that belongs to the collection of facts not the result of choice and experi- 
ment, but presented to us, through various and imperfect observations, from 
many places and through long-lapsed periods, during which all the conditions 
of observation have suffered much change, so that the facts that are presented 
for record, and those of which no account is given, are alike subject to 
certain contingent or accidental modifying conditions, but of such a nature 
as to defy our making them part of our discussion. 
So in a work which proposes to collect under one view the transmitted 
observations of the whole human race, and of all historic time on this 
particular subject, the conditions of human observation itself enter into 
the results, and our earthquake record is at once an account of these phzno- 
mena, and of the rise, progress, and extension of human knowledge and 
observational energy, and also of the multiplication and migrations of the 
human family and its progress in maritime power; in a word, at every mo- 
ment the indeterminate extent to which man has fulfilled his great destiny 
of “ replenishing the earth and subduing it,” affects every continuous record 
of his observations or his arts. 
The method of discussion followed was that of numerical analysis as to 
time, and topical analysis as to space, from which curves graphically repre- 
senting the results have been projected by the usual methods. 
One conventional arrangement has been found inevitable. It refers to 
the cases of long-continued slight shocks or tremors, occurring almost daily, 
as at Pignerol in 1808; St. Jean de Maurienne in 1839; Comrie, in Perth- 
shire, 1839-1847; and Ragusa in 1843-1850. In these the slight shocks 
recorded for each month of the disturbed period are grouped as forming one 
earthquake at the locality. Had not some such arbitrary rule been adopted, 
these comparatively insignificant, though frequently repeated exhibitions 
of seismic force (if they be such) would, when introduced in the curves, 
have given, at certain points of time, a false elevation to the abseisse, while 
the phenomena themselves are not of a character materially to modify our 
results even if excluded. 
The conclusions possible from the still vast mass of facts here brought to- 
gether, however, will, as a first generalization, be found, I apprehend, not 
unimportant. 
They may be classed under two great heads; viz. the relation of seismie 
energy to time and to space, or the distribution of recorded earthquakes 
in each. And, first,— 
