130 
NATURE 
[JANUARY 27, 1923 

end of July until about the middle of September. 
During the first part of the year the weather had 
been rather dry throughout the Archipelago. Extra- 
ordinary seismic activity occurred during the year. 
There were 151 earthquakes felt within the limits 
of the Archipelago; only two shocks, on April 28 
and August 14, were of destructive character. In 
the Central Observatory, Manila, the seismographs 
recorded 420 disturbances due to insular and distant 
earthquakes. At Butuan the seismic disturbances 
numbered 1076. 
ULTRA-VIOLET PHOTOGRAPHY OF OLD MANUSCRIPTS. 
—In a paper by Prof. The Svedberg and Hugo 
Andersson, which has just been published in the 
Photographic Journal (No. 63, 1923, pp. 30-32), a very 
instructive example is given of the use of ultra-violet 
light in photographing old manuscripts. When a 
palimpsest is illuminated with intense ultra-violet 
light it is found that those parts of the parchment 
where the old, and subsequently erased, writing was, 
have lost the power of strong fluorescence which is 
USCSADISKRALLy IA 
PVANQCINAHAC 
SAS AGH IACH 
MAATW PALA’ 
MAA UAISAN 
CSNIGACQAAIAU ARIE 
Hav ARP ab pan Ary 
VSMATRIAIp ELS 
SAB ATOMLS 
spirtaniyarly 
SUIS ATERLA RIT: 
BARDIW CMA DAL! 
Fic. 1. 





still exhibited by the untouched parts of the parch- 
ment. Kdodgel, in 1915, worked out this method for 
deciphering such parchments, and Svedberg and 
Nordlund used it later for deciphering the famous 
“Codex Argenteus’’ in the University Library of 
Upsala, and for other similar purposes. The diffi- 
culties attaching to this method lie in the very long 
exposures necessary to obtain a negative by means of 
the comparatively feeble fluorescence, several hours’ 
exposure being necessary through the filters used to 
cut off the visible light from a quartz mercury lamp. 
The Wratten department of the Kodak Company has 
recently put a new U.V. filter on the market, and by 
means of this filter, Prof. Svedberg and Mr. Andersson 
have succeeded in cutting down the exposure to 15 
minutes, with the results illustrated in Fig. 1, which 
shows the comparison between an ordinary photograph 
and the fluorescence photograph. The Wratten filter is 
superior to the Zeiss U.V. filter hitherto used for such 
purposes, in that it is much more transparent (about 
to times) in the long-wave part of the ultra-violet 
(391-344 MH). 
THE FADING oF CoLours.—An interesting problem, 
the fading of colours of objects in museums when 
exposed to light, was dealt with in a paper read by 
Sir Sidney Harmer, Director of the Natural History 
Departments of the British Museum, before the 
Royal Society of Arts on December 13. It is common 
knowledge that many colours fade when exposed to 
strong sunlight, but the relative injuriousness of 
diffused daylight and artificial illuminants is less 
NO. 2778, VOL. IIT | 


known. Experiments by Dr. Russell and Sir William 
Abney led to the following main conclusions : 
(1) fading is due to the action of light and not to 
moderate heat; (2) it does not take place im vacuo, 
i.e. in the absence of oxygen and moisture ; and (3) 
the rays of the violet end of the spectrum produce 
the greatest amount of fading” Experiments with 
various glasses devised to check the transmission of 
ultra-violet rays have been made. Some of these 
have a useful effect, but it appears that in general 
the use of tinted glasses merely delays fading and 
does not prevent it, in the case of fugitive colours. 
The best glass for the purpose had a distinct yellow 
coloration, rendering its use for cases scarcely 
practicable. As examples of the length of continuous 
exposure necessary to cause fading it is mentioned 
that the wings of certain moths showed appreciable 
fading in 10-21 days; on the other hand, the fur 
of the tiger required 175 days, and of a brown horse 
and antelope 1485 days, before there was perceptible 
change of colour. According to these experiments 
direct sunlight was about from 20 to 7o times as 
injurious as electric light, and diffused daylight 
about six times as injurious. While too much 
importance should not be attached to such figures, 
there seems little doubt that illumination by electric 
light is less liable to cause fading than natural light, 
and the question arises whether very valuable 
specimens, or those with highly fugitive colours, 
might not be lighted entirely by artificial means. 
Most artificial illuminants contain less ultra-violet 
energy than daylight. But apart from this it is 
possible that a much lower intensity of illumination 
might suffice to enable specimens to be seen. : 
STANDARDISATION OF EXPERIMENTAL TANK DaTa. 
—In view of the fact that nearly all the important 
maritime nations of the world have experimental 
tanks, the introduction of international systems for 
the presentation of results would be extremely helpful 
to experimenters and designers. Mr. Telfer, in a 
paper, ‘‘ The Presentation of Ship Model Experiment 
Data,’’ read before the North-East Coast Institution 
of Engineers and Shipbuilders, on December 8, 
discusses the existing systems of presentation and 
their relative usefulness. He points out that the 
basis of any system should be dimensionless, and that 
the units forming this basis should be international, 
besides giving results finally that can be readily 
interpreted by practical men without any arithmetical 
unravelling. Experimental work up to the present has 
been presented in widely different forms. Froude used 
expressions Speed/(Vol.)* and Power/(Vol.)i(Speed)%, 
giving results for a one cubic foot model. Taylor, on 
the other hand, expresses his results per ton of dis- 
placement. Mr. Telfer suggests that results could be 
made international by adoption of the metric system 
and presenting results for models of one metric 
ton displacement, adopting Power/(Volume)* and 
Speed/(Volume)! as the basis of the presentation. He 
also suggests the adoption of definite symbols, these 
being selected “‘from international philological: con- 
siderations, all related symbols being mnemonically 
appropriate and above all typographically simple 
rather than typographically unique.’’ Such an inter- 
national code is greatly needed. There is at present 
an awkward disregard for standardisation of symbols 
even among experimenters of the same nation. It is 
to be hoped that this present paper will help forward 
in ship model data what has already been adopted 
in aeronautical work. Before setting up an inter- 
national system such as is suggested, it would be best 
for a representative committee to inquire into the basis 
to be adopted, and also to undertake the transfer- 
ence into this system of all existing data. 
