COLLECTION AND REPRODUCTION OF THE SEISMOGRAMS, 
The intensity of the shock was so great that practically all seismographs, situated in 
any part of the world, recorded it. Shortly after the earthquake letters were addrest 
to all the seismological observatories in the world asking for copies of their seismograms 
and other necessary data, and the Commission takes pleasure in expressing its thanks 
to the directors of the various observatories, who were kind enough to send reports and 
either their original seismograms or copies, which have been reproduced in the Atlas. 
A few, however, were too faint for reproduction and have been omitted. 
‘In the great majority of cases, copies of the seismograms, and not the originals, were 
sent; and it was not thought necessary to reproduce them in facsimile, especially as the 
International Seismological Association has recently reproduced in facsimile the seis- 
mograms of the Valparaiso and Aleutian earthquakes of August 16, 1906. A very careful 
tracing was therefore made of each seismogram and this was reproduced by photo- 
lithography. Some of the seismograms, especially those made by Milne instruments, 
do not lend themselves to this method, and they have been reproduced by a gelatin 
process. Some of these were too faint in places to yield good reproductions; they were 
accordingly slightly strengthened, the draftsman keeping well in view the character of 
the instrument and being guided by the marginal records, so that the true form of the 
central record has been preserved. 
Great care has been given to all reproductions, and the characteristics of the various 
seismograms have been well brought out. 
In printing the seismograms those recording times are so placed that the time increases 
from left to right; it has not always been possible also to make the time increase from top 
to bottom, but an arrow has been placed at the beginning of the record so that this part 
can readily be found. In most cases the times are given in Greenwich mean civil time 
(G. M. T.), 0 hours beginning at midnight. Where a correction is necessary or where 
local time is used, the correction to reduce to G. M. T. is given under the seismogram, 
the total correction is always given, including the error of the clock, the parallax of the 
recording stylus, and the correction for longitude where local time was used. 
The seismograms are reproduced in their original size, except in a few instances, which 
are noted. These were cases in which they were extremely large and the copies supplied 
were from hand tracings, so that nothing was lost by the reduction; or cases in which 
the copies were already reduced. The seismograms on sheets 1 and 2 have been inad- 
vertently reduced about 2 per cent; but this is unimportant. It was desired to arrange 
the seismograms in the order of their distances from the origin, but on account of the two 
different methods of reproduction, and the greater number of plates this plan would 
require, it was given up and the seismograms arranged so as to make the smallest pos- 
sible number of plates. The seismograms from any station can readily be found from the 
list of observatories, from the contents, or from the table of contents of the Atlas. 
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