SEPTEMBER 21, 1899] 
NATURE 
491 
special branch of the subject would have had a guide 
to full and intelligible records of detail. Such references 
are nowhere given. The book is worth the extra clerical 
work that their insertion would have involved ; but as 
it stands it is of little use to any one. Who, for in- 
stance, is helped by this brief paragraph on p. 64?— 
“Concentration of sea-water.—The process is employed 
in some northern salt-works, and is more economical 
than concentration by heat.” 
LETTERS TO THE EDITOR. 
[ The Editor does not hold himself responsible for opinions ex- 
pressed by hts correspondents. Neither can he undertake 
to return, or to correspond with the writers of, rejected 
manuscripts intended for this or any other part of NATURE. 
No notice zs taken of anonymous communications. | 
Movement of Sea-Gulls with a Coming Change of 
Weather. 
IN your issue of September 7, p. 439, I read with some 
interest the note by Prince Kropotkin on the movements of sea- 
gulls upon our coasts having some connection with a coming 
change of weather; and that at Margate on Saturday, August 
26, it was noticed such a movement was going on, the gulls 
passing from west of that place to the south coast, to meet, as 
the fishermen say, a south-west wind. It may be of interest, 
and as in a measure confirmatory of such a movement going on 
just before a marked change of weather conditions, that on 
Sunday evening at 5.30 o'clock six large sea-gulls passed over 
this place, 400 feet above the sea (situated 24 miles due east of 
Cranleigh), flying in a direction south-west by south. We very 
seldom see gulls so far inland, but I have seen them before fly- 
ing in much the same course. The direction in which these 
were heading would have taken them to the coast near Ports- 
mouth, distant about thirty-five miles; and at the elevation at 
which they were flying, the English Channel was no doubt 
visible to them, for the South Downs were at the time 
particularly clear. H. H. GoDWIN-AUSTEN. 
Nore, Hascombe, Godalming, September 12. 
Thermometric Scales for Meteorological Use. 
As Mr. Buchanan has called attention to the advantages of 
the Fahrenheit thermometric scale as compared with the Centi- 
grade, I will state that at the Blue Hill Meteorological Ob- 
servatory, while the metric system has been adopted for 
research work the Fahrenheit thermometer has been retained. 
The chief reason is the same as that given by Mr. Buchanan, 
namely, the occurrence of the zero in such a place as to make 
nearly half the readings below zero. The reading of the scale 
first upward and then downward is awkward, and the averaging 
of the results troublesome, besides making in each case a 
source of error. If the Centigrade thermometer is ever adopted 
by the English-speaking nations, I would suggest that, at least 
for meteorological uses, the freezing point of water be marked 
273 on the scale, and the boiling point 373°. This would give 
meteorologists at once the temperatures which are concerned in 
the change of volume of gases, and embodied in a large 
number of the formulas used in meteorological work. At the 
same time it would for ever get rid of the troublesome inverted 
scale. In printing the results, 200 could be put at the top of 
the printed column, and the excess over 200 be printed at its 
proper place in the column. In this way most of the observed 
temperatures could be expressed in whole degrees by two figures 
as at present. 
The metric system will soon be adopted, I trust, by all the 
English-speaking peoples. Besides the advantages of the rela- 
tions of all the different portions of the system to each other, 
and the ease of converting smaller measures into fractions of 
larger measures of the same kind, every one must recognise the 
advantage of having one uniform system of measurement 
throughout the world. Almost every civilised nation except 
those speaking English have now adopted the metric system, 
and I cannot believe the English will long hold aloof. 
: . H. HELM CLayron. 
Blue Hill Meteorological Observatory, September 5. 
NO. 1560, VOL. 60] 
THE NEW LUNAR PHOTOGRAPHIC ATLAS 
M. LG£WY and Puiseux have recently communi- 
cated to the Paris Academy of Sciences? con- 
tinuations of their valuable descriptions of the unequalled 
lunar photographs they are now obtaining by means of 
the large Equatorial Coudé. As in the case of the three 
Parts of the Atlas already published, they accompany 
their descriptions with a discussion of the bearings of 
the new results obtained on the general questions of 
selenology. We have on previous occasions given an 
account of Parts i.,? 11.,° and iil, and we now give a full 
translation of the recent communications. 
The first, which deals with the description of the 
photographs contained in the fourth Part, runs as 
follows :— 
The fourth Part comprises, like the preceding ones, a 
positive on the scale of the original negative, and six 
enlargements on different scales. All these photographs, 
except one, deal with the waning moon, and for the first 
time we see the eastern edge illuminated to a certain 
extent. We propose to briefly indicate the most striking 
characteristics of the regions represented. 
Plate @ is a general photograph, in which nearly two- 
thirds of the visible hemisphere is illuminated, and distin- 
guishes itself at first sight from similar positives already 
published. Here the work of reproduction has been 
directed in such a manner as to give, as far as possible, 
the details contained in the most brilliant parts of the 
lunar disc. But we also establish an intrinsic difference 
between the eastern and western halves of the moon, so 
far as the distribution of mountains and plains is. con- 
cerned. Upto now we have seen the seas presenting 
themselves like a chain of circular basins, occupying only 
a zone of ordinary size on both sides of a great circle ; 
they now take a sudden and considerable development 
in the direction of latitude. It appears that a large 
depression encountered the first, like the Atlantic Ocean 
across the Mediterranean deeps of our globe. These de- 
pressed parts, generally of sombre colour, are not of a 
uniform shade, and the darkest spots accumulate near 
the mountainous border. There is cause to consider 
these regions as more depressed than the neighbouring 
parts of the seas, and their distribution, as they are indi- 
cated in Plates 6 and d, is in accordance with what we 
know of the ways of the submarine depths on the 
terrestrial globe. 
We have already noted, with regard to the third Part, 
the white borders which encircle Kepler and Copernicus, 
and which prolong themselves in different directions in 
long rectilinear streams. We find them here again 
illuminated more normally, and detaching themselves in 
consequence in a clearer manner. The systems of 
Euclid, Aristarchus, Olbers, Byrgius and Tycho, equally 
visible on Plate d, appear to us to be, like the first, 
depositories of volcanic cinders, carried to great heights 
by violent eruptions and disseminated by variable atmo- 
spheric currents. They imply with no less clearness 
different periods of activity, separated by intervals of 
repose. All the walled plains which serve as origin to a 
collection of such trails show under an _ oblique il- 
lumination a fairly equal uniform wall of some alti- 
tude. So soon as the sun has risen a little on their 
horizon, they shine with an intense whiteness, sometimes 
accentuated by the presence of a dark areola at the 
source of the trails. The great dimensions of Copernicus 
reveal other interesting facts ; thus we see that the white 
tint is far from being equally distributed on the whole 
length of the walled plain, that the diameter of this 
surpasses by a great deal the length of the trails, and 
1 Comptes rendus, June 26 and July 3. 
2 NavuRE, vol. lil. p. 435, 1895. 
3 [bid., vol. lvi. p. 220, 1897. 
4 [bid., vol. lix. p. 304, 1899. 
