298 
NATURE | 
[DECEMBER 14, 1916 
iron, like potassium and phosphorus, may be removed 
from the older dying organs and transferred to new 
growth. .This view is challenged by Messrs. P. L. 
Gile and J. O. Carrero, of the Porto Rico Experiment 
Station, in the Journal of Agricultural Research, 
vol. vii., No. 2. Working with rice plants grown 
normally in water culture and then transferred to iron- 
free culture solutions, these experimenters find that 
chlorosis is invariably noticed first in the new leaves, 
while the old leaves remain green, the plants dying 
from the top downwards. If iron were mobile in the 
plants after reaching the leaves, the phenomena 
should be different; iron should be transferred from 
the old to the new leaves, where growth is most 
active, and the old leaves become chlorotic first. 
Analyses of the ash from old and new leaves of young 
rough-lemon trees (Citrus limonum), grown in four 
different soils, show that the percentage of iron in the 
old is almost twice that in the young leaves. The 
authors carefully avoid any claim that the non-trans- 
location of iron is a general rule for all plants, since 
their experiments were chiefly made with rice and 
pineapples. They suggest, however, that in respect 
to mobility in the plarit iron should be grouped with 
silicon and calcium, and not with nitrogen, phos- 
phorus, potassium, and magnesium, which are gener- 
ally considered mobile. 
THE current number (December, 1916) of the School 
World contains an interesting account by Canon J. M. 
Wilson of a thirteenth-century MS. in the Worcester 
Cathedral Library. Written in Latin, it is the trans- 
lation of an Arabic text containing the definitions, pos- 
tulates, and axioms of. Euclid’s ‘‘ Elements,’’? Book I., 
together with a rhetorical abstract of props. 1-20. 
There are no figures, and, what is still more remark- 
able, there are no symbols for’ points. Thus, in 
English, the summary of prop. 1 is:—‘tTo describe 
an equilateral triangle on a given straight line. 
From the two extremities of the given line, setting off 
its length with the compass, describe two intersecting 
circles. Then from the common ‘point of the circles 
draw straight lines to the extremities of the given 
line. Then deduce the procf from the definition of 
a circle.” One of the greatest of modern works on 
pure geometry is v. Staudt’s “*Geometrie der Lage”’; 
here there are no figures, but the author uses symbols 
for points, planes, and lines. In its absence of sym- 
bols for elements, as well as its omission of figures, 
this geometrical fragment is very peculiar, and possibly 
unique. Canon Wilson says that there is room for 
figures on the margin, but he does not say whether 
any special spaces are reserved for them. Judging 
from the facsimile (p. 448), we should say that there 
were not. It may be added that the assumption used 
in the theory of parallels appears as a_ postulate 
and not as an axiom. 
In his repetition of Fizeau’s experiment on the drag 
exercised by moving matter on the ether, Prof. Zee- 
man used water flowing with a mean speed of about 
500 centimetres a second through two parallel tubes 300 
centimetres in length and 2 centimetres in diameter. 
As the two beams of light traversing the tubes pass 
along their axes it is necessary to know the speed 
of the water along the axes. In the first instance 
Prof. Zeeman calculated this speed from the mean 
speed as given by a watér meter, but more recently, 
according to two communications made to the 
Academy of Sciences of Amsterdam, which appear 
in vols. xviii. and xix. of their Proceedings, he has 
measured .the axial speed directly. His method de- 
pends on the observation of small air-bubbles intro- 
duced into the stream and illuminated by a narrow 
heam of light sent along the axis of the tube. These 
NO. 2459, VOL. 98] 
bubbles are viewed through windows in the side’ of 
the tube by reflection in a mirror rotating rapidly 
about an axis parallel to the tube. The slope of the 
line of bubbles as seen in the mirror gives their speed 
if the angular speed of the mirror is known. He ~ 
finds that the mean speed in his short pipes is 
of the speed at the axis, while, according to the 
measurements of Stanton-and Pannell at the National 
Physical Laboratory, the mean is o-82 of the axial 
speed for water moving at the same speed in long 
pipes of this diameter. ; 
Messrs. ConsTABLE AND Co., Lrp., announce the 
early publication of a translation, by J. H. Johnson, 
of Jean Rey’s “The Range of. Electric Searchlight 
Projectors.” The work will embody the investigations 
and tests carried out by the author in various parts of 
the world under actual working conditions. It will 
contain a number of diagrammatic illustrations. 
To those who are interested in Russia, Catalogue 
No. 370, just issued by Mr. F. Edwards, 83 High 
Street, Marylebone, should appeal, for it is largely 
composed of particulars of works relating to the Rus- 
sian Empire. Another section deals with books con- 
cerning the United States, Canada, the West Indies, 
Central and South America, and a third with those 
on the western counties of England. 
OUR ASTRONOMICAL COLUMN. 
Tue LoncirupE or WasHincton.—tThe first direct 
determination of the longitude of Washington, referred 
to Paris, has lately been made by American and 
French astronomers with the aid of wireless signals be- 
tween the Eiffel Tower and the naval station at Radio, 
Va. 
given in Appendix to Publications of the U.S. Naval 
Observatory, second series, vol. ix. The antennz at 
the two stations were adapted for the use of practically 
the same fundamental wave-length, namely, 2150 
metres. Notwithstanding the great distance of 3840 
miles between the two stations, the signals received at 
Paris are stated to have been very clear, though those 
received at Radio were rather feeble. The final result 
Washington—Paris is given as 5h. 17m. 36-653s. 
+o-0031s.; and for Washington-Greenwich as 
5h. 8m. 15-721s.t0-014s. The value of the latter pre- 
viously derived by the U.S. Coast and Geodetic Sur- 
vey, and quoted in the Nautical Almanac, was 
sh. 8m. 15-78s. It is interesting to observe that the 
mean double-transmission time was 0:0429S. +0-0029s., 
corresponding to a velocity of transmission of 
179,000 + 12,000 miles per second. 
A number of American observatories also made 
arrangements to receive the time signals from Radio 
and to utilise them for determinations of their longi- 
tudes from Washington. 
Tue Varias_tE Nesuta N.G.C. 2261.—Another case 
of a nebula of variable form has been found by E. P. 
Hubble in N.G.C. 2261 (Astrophysical Journal, 
vol. xliv., p. 190). The nebula in question is the finest 
known example of the rare ‘‘cometic’’ type, and is - 
situated in R.A. 6h. 32m., declination +8° 51’. Its 
form is nearly that of ar equilateral triangle with a 
sharp stellar nucleus at the extreme southern point, 
this nucleus forming the irregular variable star 
R_ Monocerotis. A photograph taken during last 
winter by Mr. Hubble with the 24-in. reflector of 
the Yerkes Observatory showed decided changes in 
the nebula when compared with a plate taken eight 
years earlier by F. C. Jordan with the same instru- 
ment. Confirmation of the variability was found in a 
photograph taken by Isaac Roberts in 1900, and in 
Full details of the extensive observations are 
