Marcu 19, 1914] 
NATURE 
3 
which has led to such great changes in our views 
concerning the theory of cyclones, etc., it is reasonable | 
to suppose that still further investigation in this direc- 
tion would lead to further advances, and that, there- 
fore, the work is one which deserves encouragement 
in a practical way. My own plea, which gave rise to 
this discussion, was for better daily charts. At the 
present time millions of observations are practically 
buried so far as the individual meteorologist is con- 
cerned. A large part of these could be put on the 
charts and rendered available for all. My suggestion 
as to the Daily Weather Charts was, that the wind 
provinces should be put in. I found that, even with 
the information now published, it was possible to do 
this with fair accuracy during a period of about ten 
weeks. With a few more wind observations plotted 
on the diagrams it would be possible to do this accu- 
rately. Then the isotherms and humidities of each 
wind province could be put on the chart. The isobars 
run from one wind province to another in continuous 
curves. This is not the case with the isotherms— 
they terminate more or less abruptly, as do the 
humidity curves, at the borders of the wind provinces. 
The winds and isotherms taken together, therefore, 
render it possible to draw the wind provinces with 
some accuracy. 
It seems probable that daily charts with all the 
details that have been enumerated plotted on them 
would not entail great expense, would very likely 
teach us a great deal concerning cyclones and anti- 
cyclonic areas, and prevent so much valuable detail of 
atmospheric change being buried on the shelves of our 
institutions and societies. 
R. M. DEeELey. 
Abbeyfield, Salisbury Avenue, Harpenden, 
February 28. 
The Doppler Effect and Carnot’s Principle. 
So many objections, based on the Doppler effect, 
have been made to my application of Carnot’s prin- 
ciple to each particular frequency in full radiation, 
that it seems necessary to show that the two methods 
are not mutually inconsistent. 
According to the Doppler effect, when a beam of 
light g, per sq. cm. per sec. moving with velocity c 
is directly reflected by a mirror moving with velocity 
nc in the same direction, the frequency of every com- 
ponent in the beam is reduced by reflection in the 
ratio (1—n)/(1+mn), which according to Wien’s dis- 
placement law is also the ratio T,/T, of the tempera- 
tures of the reflected beam q, and the incident beam q,. 
‘The net expenditure of energy by the radiation per sec. 
per sq. cm. is qi—q., which reduces to 4nq,/(1+n)’, 
since the energy density varies on reflection as the 
square of the frequency. Part of this energy 
(g.+4q.)n, is left in the space nc vacated by the mirror 
per second. The remainder, 2nq,(1—n)/(1+n), is 
equal to the work done by the radiation pressure , 
namely, puc per sec. per sq. cm. We thus obtain 
p—29,1,/el,—29,0,/cl,=2q,q./¢, which is true for 
every component separately, and gives in the limit 
p=2q/c when the motion is slow, and the incident 
and reflected beams become equal. 
The energy left in the medium, (q,+4q.,)n, does not 
give rise to a volume of stationary vibration, wnc, 
where u=p=2q/c, as commonly assumed, because the 
frequencies of each component before and after reflec- 
tion are essentially different on account of the Doppler 
effect. In order to find the stationary vibration, or the 
intrinsic energy-density wu in the state of equilibrium, 
we must combine each incident ray with a reflected ray 
of the same frequency, before taking the limit. For 
any component q in the incident beam, the energy- 
stream of the component having the same frequency 
NO. 2316, VOL. 93] 
in the reflected beam is q—(dq/dT),dT, where 
dT=2nT when n is small, and (dq/dT), is the rate 
of increase with temperature of an energy-stream of 
constant frequency v. The net energy supplied of a 
particular frequency is 2nT(dq/dT), per second, and is 
equal to (w+p)nc. But since p=2q/c, this reduces 
in the limit to exact agreement with Carnot’s prin- 
| ciple, T(dp/dT),=u+p; which applies correctly to the 
equilibrium state. H. L. CALENDAR. 
Ligament Apparently Unaltered in Eocene Oysters. 
DurinG the examination of some large specimens 
of Ostrea bellovacina, Lam., from the Woolwich beds, 
sent on February 20 to this office by Mr. A. G. Davis, 
of Beckenham, a very interesting case of the preserva- 
tion of what appears to be organic tissue in an un- 
altered state has come to light. 
The ligament in the two specimens examined has 
a remarkably fresh appearance, and in its aspect 
and texture compares so closely with that of a recent 
oyster as to suggest that the fossil specimen has under- 
gone no change, except that it is somewhat softer and 
the fibres are less coherent. 
The whole of the ligament has been removed from 
one specimen and preserved in spirit, and a portion 
will be embedded in paraffin and sections cut for 
microscopical examination. 
The specimens were obtained from the lowest bed 
of the following section :— 
Excavation for Sewer in the High Street, Beckenham. 
Soil Sit Onin. 
Buff coloured sand with scattered 
Oldhaven P pe cleles : | 
oe ale grey sand with seams of clay, ; 9 ft. o in. 
Blackheath: the lower part ferruginous, with 
Bee wood and iron pyrites 
Cyrena and Ostrea bed with some)|1I ft. oin. to 
pebbles Jette Onm. 
Bluish grey clay with broken Cyrena | Ate Ga 
Weaolwich Bluish grey sandy clay with Ostrea Jf : ; 
Bidet Bluish grey mudstone and muddy | Baton 
sand slightly cemented. 
Modiola, ete. 
See fut through 
The preservation of organic tissue in fossils is so 
extremely rare that this instance is worth recording. 
Further examination is being made. 
R. W. Pocock. 
Geological Survey, Jermyn Street, S.W., March 13. 
Experiments Bearing upon the Origin of Spectra. 
IN connection with Prof. Strutt’s letter under the 
above title in NaTurE of March 12, it may be of interest 
to direct attention to some previous work of Prof. 
Lenard’s which contains results bearing on the same 
subject. Lenard (Annalen der Physik, vol. xvii., 
1905, p- 197), as a result of a study of the light emission 
of the electric are and the Bunsen flame containing 
metallic salts, showed that the principal and sub- 
ordinate series are emitted by different distinct regions 
of the luminous source, and are thus due to different 
centres of emission. Further, he demonstrated that 
the centres emitting the different series behave differ- 
ently in an electric field, and came to the conclusion 
that while the centres which emit the principal series 
are neutral metallic atoms (as has been also contended 
by Wien for the canal rays), the centres of the sub- 
ordinate series are atoms rendered positive by the loss 
of one or more electrons, one for the first series, two 
for the second, and so on. This theory is strikingly 
borne out by Prof. Strutt’s experiments, all of which 
seem to be explicable by it; in any case, this inde- 
pendent confirmation seems to place beyond doubt 
the different electrical state of the centres emitting 
the different series. E. N. pa C. ANDRADE. 
University of Manchester, March 13. 
