40 
NATURE 
[SEPTEMBER 14, I916 
I <<< 
Kollegorsky describing a series of experiments on the 
mechanism of photosynthesis by means of a Jumin. 
escent bacterium (Photobacterium italicum). Taking 
as the subject of their experiments two plants of 
strongly contrasted habits, Aspidistra elatior and 
Bambusa verticillata, they give the following summary 
of the results of their researches :—(1) The working 
out of a new method of the quantitative study of 
photosynthesis by the aid of luminescent bacteria. 
(2) It is established that the luminous intensity indis- 
pensable for the decomposition of carbonic acid 1s the 
same for plants which vary ecologically. (3) It is 
shown that the luminous intensity effecting the libera- 
tion of oxygen in photosynthesis may be in the case 
of plants possessing special light-collecting apparatus 
much lower than for those not so provided. 
Mucu valuable meteorological and magnetical work 
is being done at Hongkong, and the report of the 
director, Mr. T. F. Claxton, has just reached this 
country. Continuous photographic records are being 
maintained showing the variations of barometric 
pressure and temperature, and there are daily auto- 
matic records of the direction and velocity of the 
wind, the amount of rain, duration of sunshine, and 
the relative humidity of the air. Eye observations of 
many of the elements are also made each hour. 
Attention is directed to the defect of wind velocity 
which has been noticed for several years past, and 
this has hitherto been attributed to instrumental 
rather than climatic causes. The decrease has 
occurred more or less steadily from 1884 to 1915. A 
similar defect in the wind velocity has been noticed 
at the Royal Alfred Observatory, Mauritius. The 
director of the Mauritius Observatory, in a recent re- 
port, remarks: ‘‘There is now reason to believe that 
the low velocities during the years 1901-11 are almost 
entirely climatic, and due probably to a_ periodic 
oscillation in this element.” At Hongkong the 
decrease in the mean velocity of the wind is said to 
be far greater than the secular variations in any other 
element, and must, in the opinion of the director, at 
least in part, be attributed to instrumental causes. 
Tue Journal of the Franklin Institute for August 
contains a paper by Prof. Kennelly and Messrs. 
Achard and Dana, of the Massachusetts Institute of 
Technology, dealing with the increase of the resist- 
ance of standard forms of track and contact rails 
when the current through them is an alternating 
instead of a direct one. The currents used were 
sinusoidal of frequencies from 25 to 60 per second, 
and varied in root mean square values from 10 to 800 
amperes. Both the alternating potentiometer method 
of comparing voltages down the rail and a manganin 
strip in series, and the dynamometer method of 
measuring the current and the active and reactive 
components of the voltage down the rail, were found 
satisfactory. The ratio of the resistances with alter- 
nating and direct currents increased with the magni- 
tude of the currents to a maximum, at which it re- 
mained in most cases, but in a few cases it diminished 
again. The ratio, when a maximum, had values about 
7 for track and 12 for contact rails at a frequency 25, 
and varied nearly as the square foot of the frequency. 
The best form of rail is discussed, and it is shown 
that theory reproduces the observations with a fair 
degree of accuracy. 
WE have received from Mr. Oertling a copy of his 
recently issued catalogue of balances and weights. 
This firm claims that all its balances, -ete., are, and 
always have been, manufactured in London. On com- 
parison of the present list with that issued in 1909, we 
seven years ago. appear in the new catalogue; the _ 
prices, however, have increased in a proportion vary- 
ing from 19g to 26 per cent., presumably owing 
to the general increase in cost of commodities — 
and labour due to the war. Several balances designed 
especially for the Royal Arsenal, Woolwich, the Air- 
craft Factory, the Admiralty, 4nd for explosives fac 
tories now appear for the first time. One of these is 
specially adapted for rapidity of weighing. Except in’ 
one item the weights are listed precisely as in the 
1909 catalogue. The exception is that a cheap set has: 
been introduced for school use. The increase in price 
of the sets of weights is not so large, varying from- 
11 to 20 per cent., except in one instance. ' 
We learn from the Engineer of September 1 that 
the Reclamation Service of the United States has 
recently finished at Elephant Butte, about twelve miles 
west of Engle, the dam which forms the keystone 
of its great water storage project in New Mexico. 
The work, which has been under construction since 
1911, is designed with the object of providing water 
for irrigational purposes, by means of the storage of 
the flood waters of the Rio Grande, which are to be 
distributed at various points downstream, so that a 
total area of 185,000 acres will be brought under treat. 
ment. The district has a general elevation of 3700 ft. 
above sea-level; the climate is mild, and the tempera- 
ture fairly equable throughout the year; the annual 
rainfall is about 10 in. It is thus a suitable location _ 
for husbandry, if the soil be adequately watered. The 
lake, or reservoir, which has been formed by dam- 
ming the cafion of the Rio Grande at Elephant Butte, 
has, when full, a storage capacity of 862,200 million 
gallons, a surface area of 42,000 acres, a maximum 
length of 45 miles, a maximum depth of 193 ft. (the 
average is one-third of this), and a shore line of some- 
thing above 200 miles. The dam contains 610,000 
cubic yards of masonry, estimated to weigh about a 
million tons. It is not quite so imposing a structure 
as the two earlier dams built by the same service, but 
it is nevertheless a notable engineering achievement, 
and the outlay of about 1,000,000l. on the scheme will 
probably be considered but a moderate price to pay 
for the benefits which are expected to be derived from 
the undertaking. 
Mr. A. T. Hopwoop writes to say that the display 
of aurora described by Mr. Denning in Nature of 
August 3, was visible in Manchester about 11 p.m. 
(Summer Time) on the night of August 26. 
Economic pamphlets on ‘‘The House-Fly as a 
Danger to Health,” ‘‘The Louse and its Relation to 
Disease,” and ‘Fleas as a Menace to Man and 
Domestic Animals,’’ have already been published by 
the British Museum (Natural History), South Ken- 
sington. Three further pamphlets on, respectively, 
“Mosquitoes in Relation to Disease,’ ‘‘ The Bed-Bug 
and its Relation to Disease,’’ and ‘Ticks, ete., In- 
jurious to Man,”’ are in preparation. ; 
OUR ASTRONOMICAL COLUMN. 
MEASUREMENT OF CLOSE SOLAR LinEs.—As a pre- 
liminary to the determination of the wave-lengths of 
solar lines in international units, and in connection with 
the search for mutual influence between neighbouring 
lines, Dr. C. E. St. John and Miss Ware have made 
a careful study of the difficulties attending the precise 
measurement of closely adjacent lines (Astrophysical 
Journal, xliv.,°p. 15). Micrometric measurements 
were made by at least two observers upon a series 
notice that with few exceptions all the balances listed | of spectrograms representing the first five orders of 
NO.. 2446, VoL. 98] 
