FEBRUARY 19, 1914] 
clusion that waves incident on the earth’s surface 
would suffer. reflection accompanied by splitting up 
of the simple condensational or distortional waves 
into two sets, one of each kind, so that, at distant 
stations, the arrival of the direct waves would be 
complicated by the arrival of reflected waves, which 
had travelled one part of their course as condensa- 
tional, and the other as distortional, waves. The 
critical point at which confusion from this cause would 
arise is at about 120° distant from the origin, and the 
disappearance of the second phase, as a recognisable 
feature in seismograms at greater distances, is attri- 
buted tothis cause; the records, which I had accepted 
as possibly indicating a diminished and retarded 
appearance of this phase, being interpreted as the 
arrival of the reflected distortional waves. 
With regard to this explanation, I may say that 
the reality of the reflected waves, though accepted by 
many seismologists, and practically universally by the 
Germans and the whole school dominated by the 
influence of their work, still seems to me far from 
being established. The theory is based on _ the 
assumption of a globe of uniform constitution bounded 
by a reflecting surface, but this does not exist in 
nature, for the outer crust of the earth is composed 
of material which was long ago shown, I believe 
first by Prof. Rudzki in 1899, to be composed of 
material which cannot transmit simple condensa- 
tional and distortional waves, but transforms them 
into more complex forms of wave motion. Nor have 
we reason to suppose that the lower surface, of this 
outer crust presents a definite surface of contact be- 
tween two media of different character, from which 
reflection could take place; rather it is to be expected 
that the transition is gradual and that the simple 
forms of wave motion, which can be propagated 
through the central portion of the earth, would be 
gradually converted into more complex forms, and 
become extinguished, in the surface layers. On the 
observational side, too, the case is not conclusive, for 
though the presence of reflected waves in the record 
has been claimed, more particularly in the case of 
earthquakes originating in the Malay Archipelago 
and beyond, their presence does not seem to be con- 
stant, nor by any means so conclusively established 
as the reality and distinctness of the first- and second- 
phase waves. 
_ Accepting, however, the reality of reflected waves 
and the interpretation, offered by Prof. Wiechert, of 
the records accepted by me, with considerable hesita- 
tion, as possibly representing the arrival of the second- 
phase waves, it does not afford a sufficient explana- 
tion of the absence of the record of the arrival of 
the second-phase waves, travelling along the direct 
course from the origin, in seismograms from stations 
at and beyond 12,000 km. from the origin. This 
phase is well represented, and usually conspicuous, 
especially in the records of horizontal pendula with a 
moderate rate of travel of the recording surface, and 
up to the limiting distance, at which it disappears, 
forms a feature in the seismogram which should be 
recognisable even if superimposed on the record of 
reflected waves; for. apart from the hypothesis of a 
central core of material less capable of transmitting 
these waves, there is no reason for anticipating a 
diminution in the amplitude of the record at greater 
distances, but rather the reverse. 
The length of wave path of the waves emerging 
at the antipodes of the origin is certainly greater, 
about 12,750 km., as against about 9500 km. for waves 
emerging at 10,000 km. from the origin, but, on the 
other hand, two wave paths starting directly downwards 
with a divergence of 1° will issue on the surface at 
a distance of about 222 km. apart, and two wave 
NO. 2312, VOL. 92] 
NATURE 
685 
paths starting at an inclination of about 70° to 74° 
downwards from the horizontal and a divergence of 
1° will reach the surface at some 10,000 to 12,000 km. 
from the origin, and at a distance of about 500 km. 
apart. Setting these two against each other, we 
have, on one side, the increased energy due to a more 
than twofold concentration of wave paths, and, on 
the other, the greater absorption due to about 30 per 
cent. greater length of wave path, the former of 
which should more than counterbalance the latter, so 
that the record of the direct waves ought to be more 
conspicuous at greater distances than between 10,000 
and 12,000 km., up to which it is easily recognisable. 
I have examined most of the records obtained at 
greater distances previous to 1906, and some of later 
date, but have failed to discover the second phase, 
and it seems reasonable to suppose that this may be 
explained by the wave paths to these greater distances 
having encountered a different form of matter which is 
less capable of transmitting the second-phase waves 
from that traversed by the waye paths which do not 
descend so deeply into the interior of the earth. 
Though this letter has run to a considerable length, 
I hope you will allow me space to refer to another 
passage in Dr. Walker’s book, on p. x. of the intro- 
duction, where he refers to a paper by me (published 
in Phil Trans., 1900) as the first application of the 
well-known theory of longitudinal and_ transversal 
waves to Milne seismograms. Had Dr. Walker veri- 
fied his reference he would have found that the paper 
has nothing to do with Milne seismograms, and that 
it was the first published demonstration of the three- 
fold character of the wave motion recorded at a 
distance from the origin, and incidentally an explana- 
tion of the failure of earlier attempts to interpret the 
records in terms of the two forms only, of longitudinal 
and transversal waves. R. D. OLDHAM. 
The Evidence for Spontaneous Generation. 
In reference to the letter of Profs. Farmer and 
Blackman in Nature of February 12, it seems needful 
to state that only two of my tubes were opened in 
their presence. One of them showed,.as I had 
predicted, bodies very closely resembling Torula, in 
largenumbers. They were not, however, typical Torule, 
such as are represented in Figs. 1, 3, and 5, of my 
communication published in Nature of January 22, 
and I am prepared to admit some doubt as to their 
nature. The other tube showed, as others of the same 
series had done, peculiar spores, which when shown 
together with their mycelium (as in Fig. 2) to an 
eminent fungologist, were said by him to belong to 
a mould allied to the genus Oospora. He had no 
doubt as to its nature; and I am certain that these 
moulds must have grown within the tubes after their 
sterilisation, in one case to the extent of producing, 
after sixteen months, two tufts plainly visible to the 
naked eye. 
I am glad to learn that one of the colleagues of 
Profs. Farmer and Blackman is repeating my experi- 
ments, and trust he will, after a time, be able to solve 
their doubts. H. Cuariron BastIAn. 
The Athenzum, February 13. 
The Wearing of Birds’ Plumage—A Woman's Protest. 
_ Ir is very gratifying to find how earnestly, the best 
papers are now taking up the cause of the various 
beautiful birds hitherto so cruelly .and_ callously 
slaughtered for the sake of their plumage. The 
_ dealers in feathers seem to think that because they 
have embarked in that particular trade it must never 
