114 
THE last number of the Royal Geographical Society of 
Antwerp (tome ix. 5¢ fascicule) contains a paper by M. van den 
Gheyn on the European origin of the Aryas, a discussion of 
recent researches on this subject, especially of the works of 
Schrader, Pena, von Loher, Roth, Geiger, and Ujfalvy. The 
author, while regarding the subject as open to discussion, thinks 
that the probabilities are in favour of an Asiatic origin. Dr. 
Haine writes on the manners of the Californian Indians, amongst 
whom he passed some time about 1850. M. August Thys con- 
tributes a brief account of an early Flemish navigator, Dietrich 
Paesschen, who made several voyages to the Levant about 1511 ; 
and M. Baguet describes Steinen’s late journey on the Xingu. 
An instalment of the report of the commission to study the 
Scheldt concludes the number. 
THE expedition which the Norwegian Government dispatches 
this summer to the coast of Finmarken, to which we have pre- 
viously referred, has for its chief object to ascertain whether 
there are banks or fishing grounds far from the coast, a circum- 
stance which has never been ascertained, but which would be of 
great value if proved. Hitherto all fishing has been confined to 
the shore, but, judging from what is the case further south in 
Norway, such a discovery is very likely. 
ON May 27 the Arctic steamer A/er? sailed from Halifax with 
a scientific expedition for Hudson’s Bay, to examine its harbours 
and the facilities that exist fora trade route from the Western 
Territory to Europe. 
ARTIFICIAL EARTHQUAKES 
Outs recently we noticed a paper by Prof. Milne, of Japan, 
which contained exhaustive records of nearly 250 earth- 
quakes that occurred in that country in two years, and which 
was an earthquake history of Northern Japan during that period. 
We have now before us another paper from the same indefatigable 
mvestigator, also on earthquakes, but on a totally different 
branch, viz. seismic experiments—in other words, on artificial 
earthquakes. These experiments are so original in their incep- 
tion, and in some respects so unexpected in their results, that 
they are worth describing at some length. The paper, which 
was read before two successive meetings of the Seismological 
Society of Japan towards the close of last year, covers over 
eighty octavo pages, and contains several illustrations; but it 
will be possible to extract its principal results in a comparatively 
short space, There were in all ten series of experiments, carried 
on over three years. The object was to study phenomena con- 
nected with earth-vibrations produced either by some explosive 
like dynamite, or by allowing a heavy weight to fall irom a 
height. Each set of experiments involved several weeks’ pre- 
paration ; amongst the chief difficulties to be overcome were the 
procuring, transporting, and storing dynamite, putting the 
observing-stations in telegraphic connection, arranging the 
firing apparatus, making electric fuses, and the like, and doing 
all this in the midst of a populous city. These initial difficulties 
could never have been overcome but for the assistance of various 
departments of the Japanese administration, and it is pleasing 
to notice the help which Japanese officials freely render Prof. 
Milne in his interesting and important work in the field of 
seismic science. Nevertheless, he warns his readers at the out- 
set that his experiments were such that it is hardly just to expect 
them to be carried out satisfactorily by a private individual ; the 
trouble, expense, danger, and magnitude of the arrangements 
which they involve make them fitter undertakings for an army 
corps. 
The only guiding data which he had when he commenced 
were the results obtained by the late Mr. Robert Mallet and by 
Gen. Abbot. These referred only to the velocity with which 
earth-vibrations were propagated, and in taking diagrams of 
earth-motion he was therefore entering upon new ground, and 
therefore continually encountered new results. Sometimes it 
was found that the instruments employed required modification 
before satisfactory records could be obtained 3 at other times the 
records which were obtained gave indications of new lines of 
investigation, to pursue which new apparatus would be needed, 
and soon. Hence many of his results, he observes, can only be 
regarded as provisional ; for example, those which relate to the 
velocities of normal and transverse vibrations. The experiments 
were carried out, as far as circumstances would permit, in differ- 
ent soils, the chief agents employed being heavy weights of 
1700 Ibs, and upwards dropped from heights up to 40 feet, and 
NATURE 
different quantities of dynamite exploded in cavities of varying 
depths. 
mographs. 
experiments are described with the utmost detail, illustrated by 
[Fune 4, 1885. 
The effects of these were observed with different seis- 
The observations thus made in the ten series of 
numerous plans and tables, under their appropriate heads. Prof. 
Milne sums up his results under a succession of heads, and the 
most important of them are given below. He observes, how- 
ever, that in reading these conclusions it must be remembered 
that they only refer to experimerts performed in certain kinds of © 
ground. 
Effect of Ground on Vibration.—Hills have but little effect in 
stopping vibrations, but excavations exert considerable influence 
onthem. In soft, damp ground it is easy to produce vibrations 
of large amplitude and considerable duration; in loose, dry 
ground an explosion of dynamite yields a disturbance of large — 
amplitude but of short duration, while in soft rock it is difficult 
to produce a disturbance the amplitude of which is sufficiently 
great to be recorded on an ordinary seismograph. 
General Character of the Motion.—The pointer of a seismo- 
graph with a single index first moves in a normal direction, after 
which it is suddenly deflected, and the resulting diagram yields — 
a figure partially dependent on the relative phases of the normal 
and transverse motion, which phases are in turn dependent upon 
the distance of the seismograph from the origin of the disturb- 
ance. <A bracket seismograph indicating normal motion at a 
given station commences its indications before a similar seismo- 
graph arranged to write transverse motion. If the diagrams 
yielded by two such seismographs be compounded, they yield 
figures containing loops and other irregularities not unlike the 
figures yielded by the seismograph with the single index. Near 
to an origin the first movement will be in a straight line out- 
wards from the origin ; subsequently the motion may be elliptical, 
like the figure 8, and irregular. The general direction of the 
motion is, however, normal. Two points of ground only a few 
feet apart may not synchronise in their motions, and earthquake 
motion is probably not a simple harmonic one. : 
Normal Motion.—Near to an origin the first motion is out 
wards ; at a distance from the origin the first motion may be in- 
wards, the nature of the movement being dependent probably 
on the intensity of the initial disturbance and on the distance of 
the observing station from the origin. At a station near the 
origin the second or third wave is usually the largest, after which 
the motion dies down very rapidly in its amplitude, the motion 
inwards decreasing more rapidly than the motion outwards. 
Roughly speaking, the amplitude of normal motion is inversely 
as the distance from the origin. As a disturbance radiates, the 
period of oscillation increases, until finally it becomes equal to 
the period of the transverse motion. It may thus be inferred 
that the greater the initial disturbance the greater the frequency 
of the waves. A wave which appeared single at one observing 
station had split up into two by the time it reached the second. 
At stations near the origin the motion inwards is greater than 
the motion outwards; but at a distance the two motions are 
practically equal. At a station near the origin the period of the 
waves is at first short, but it becomes longer as the disturbance 
dies out. The semi-oscillations inwards are described more 
rapidly than those outwards. 
Transverse Motion.—The laws governing the transverse 
motion are practically identical with those which govern the 
normal motion, the only difference being that in the case of 
normal motion they are more clearly pronounced. Near to an 
origin the transverse motion commences definitely but irregu- 
larly ; the first two or three movements are decided, and their 
amplitude slightly exceeds that of those which follow, but it 
decreases as the disturbance radiates at a slower rate than that 
of the normal motion. The period increases as the disturbance 
radiates, and decreases as the latter begins to die out. 
Relation of Normal to Transverse Motion.—Near to an origin 
the amplitude of normal is much greater than that of transverse 
motion, and as a disturbance radiates the amplitude of the latter 
decreases at a slower rate than that of the former, so that at a 
certain distance they may be equal. 
Maximum Velocity and Intensity of Movements.—An earth- 
particle usually reaches its maximum velocity during the first 
inward movement, but a high velocity is sometimes attained in 
the first outward semi-oscillation. The value 
_—_——— I —cos#@ 
V2=—4 Ip 2 SF ) 
SENG +P X a 
used by Mallet and other seismologists to express the velocity 
