NoveMBER 12, 1896] 
NATURE 
4I 
of Northern India. The chief features of the air movement in 
the hot weather months of March, April, and May are: (1) A 
feeble motion during night time, increasing rapidly to about 
2h. p.m., and, under favourable conditions, blowing almost with 
the force of a gale during the next two or three hours ; (2) intense 
dryness and excessive temperature, in which the humidity 
occasionally falls as low as two or three per cent., and the shade 
thermometer ranges between 105° and 115°; (3) clouds of dust, 
which give a peculiar reddish glare to the sunlight. Mr. Eliot 
shows, from careful comparisons of hourly observations of the 
various elements, that the more important features of the hot 
winds are practically identical with the winds of the cold weather 
months, the difference of their characteristics being chiefly due 
to the altered climatic conditions of the period. 
THE United States Naval Observatory stands in a reservation 
of seventy acres. The magnetic buildings are on a small knoll 
surrounded by a deep ravine, and the only disturbances to which 
the magnetic observations are subject arise from an electric rail- 
road, trolley system, at a distance of 1375 feet from the in- 
struments. The ravine appears to diminish the effect of the 
railroad, for neither the declination nor the horizontal force 
instrument shows evidence of disturbance, though the vertical 
force records are slightly affected. Appendix I. to Washington 
Observations, 1894, is devoted to the magnetic work at the 
Observatory during that year by Lieut. C. C. Marsh. All the 
records are tabulated in periods of 26°68 days, instead of the 
calendar months, the calendar followed being that drawn up by 
Prof, Frank Bigelow. This plan has been adopted with the 
view of further studying the relation between the sun and the 
earth’s magnetism. Several plates accompany Lieut. Marsh’s 
report ; and among the subjects illustrated by them are the 
Observatory grounds and buildings, composite curves of declina- 
tion and horizontal force, curves of diurnal variations of the 
magnetic elements, and curves of hourly and monthly disturb- 
ances of the declination. 
THE atomic weight of magnesium has recently been re- 
determined with great care by Prof. Richards and Mr, Parker, 
of Harvard, and an account of their results appears in the 
current numbers of the Proceedings of the American Academy 
of Sciences and the Zeztschrift fiir anorganische Chemie. The 
previous determinations of the atomic weight of this element 
showed a remarkable inconsistency until the year 1884, when 
Marignac recorded the results of a large number of closely con- 
cordant experiments pointing to the number 24°37. The accuracy 
of this number has now been confirmed by Messrs. Richards 
and Parker. The method selected was the analysis of mag- 
nesium chloride. The salt was prepared, with great precautions, 
from the double magnesium and ammonium chloride by heating 
in a current of dry hydrogen chloride ; it was then transferred 
to a weighing tube, without the possibility of contact with 
moisture, and the chlorine precipitated by silver nitrate, either 
gravimetrically or volumetrically. The results of four series of 
very concordant experiments give the number 24°362 as the 
atomic weight of magnesium when oxygen is taken as 16°00, or 
24°179 if oxygen be taken as 15°88. 
In the Zeetschrift fiir Elehtro-chemie for October 5, Messrs. 
E. J. Constam and A. von Hansen describe the preparation of 
potassium percarbonate by the electrolysis of a solution of 
potassium carbonate. It may be assumed that the alkali car- 
bonates, like the salts of other dibasic acids, dissociate in very 
concentrated solutions more or less completely into the ions 
+ 
M and MHCOs, the latter may, under favourable circumstances, 
combine, at the moment of their separation at the anode, to 
‘NO. I411, VOL. 55. 
me 
‘ 
| 
form a percarbonate. In order to test this view, the authors 
have electrolysed a strong solution of potassium carbonate. At 
ordinary temperatures oxygen is evolved at the anode, and 
potassium bicarbonate precipitated ; as the temperature falls the 
evolution of oxygen slackens, and at — 10° ceases almost entirely, 
a bluish amorphous powder appearing in place of the potassium 
bicarbonate. The best results are obtained with a saturated 
solution of potassium carbonate at temperatures not higher than 
—15°. The current density (from 1 to 300 amperes per square deci- 
metre) appeared to have little effect on the yield. The bluish 
precipitate is rapidly decomposed by water at the ordinary tem- 
perature, and must, therefore, be rapidly filtered off, dried on 
porous porcelain, and finally over phosphorus pentoxide. It 
then forms a bluish white, amorphous, hygroscopic powder. 
It loses carbon dioxide and oxygen when heated ; in ice cold 
water it dissolves without decomposition, but the solution evolves 
oxygen at the ordinary temperature. It liberates iodine from 
potassium iodide or hydriodic acid, oxidises lead sulphide to 
sulphate, decolourises indigo, reduces manganese and lead 
peroxides, and evolves oxygen when treated with silver oxide. 
Dilute solutions of caustic potash or of sulphuric acid decompose 
it with formation of hydrogen dioxide. 
THE additions to the Zoological Society’s Gardens during the 
past week include two Chacma Baboons (Cynocephalus por- 
cartus, 8 2) from South Africa, presented by Captain Baker ; a 
Grand Galago (Ga/ago crasstcaudata)) from East Africa, pre- 
sented by Mrs. Le Poer Richardson; a One-streaked Hawk 
(Melierax monogrammicus) from West Africa, presented by Mrs. 
Palmer ; an Oyster-catcher (Hematopus ostralegus), European, 
presented by Miss Beatrix Martin; two Ortalan Buntings 
(Emberiza hortulana), British, presented by Mr. John Young ; 
a Black-eared Marmoset (Hefale penzce//ata) from South-east 
Brazil, two Choughs (Pyrrhocorax graculus), British, deposited ; 
two Black Swans (Cygnus atratus) from Australia, two Cos- 
coroba Swans (Cygzus coscoroba) from Antarctic America, 
purchased. 
OUR ASTRONOMICAL COLUMN. 
Mars.—A Kiel telegram, dated November 11, gives us the 
following information. ‘‘Mars, Trivium Charontis double 
November 10. Flammarion.” 
Trivium Charontis is not acanal, but one of those ‘‘ oases,” as 
Lowell terms them. It forms the meeting point of no less than 
nine canals, namely: Orcus, Erebus, the twin Hades, Styx, 
Cambyses, Cerberus, Laestrygon and Tartarus. The observa- 
tion above referred to is of importance in that Lowell 
seems never, as far as we know, seen them double. 
He defines them as being regular both in position and 
shape. When they form the point of intersection of 
single canals they appear as round spots, but in the case of 
double canals ‘‘they look like rectangles with the corners 
rounded off.” The most striking case he noticed was the very 
oasis, Trivium Charontis, that is in question. Lowell found 
also that the oases ‘“‘ grew” as the canals appeared to grow, so 
that this observation of Flammarion may be of a special interest 
as regards the development of this, the largest Martian oasis. 
ce 
EPHEMERIS FOR COMET PERRINE.—A postal card from 
Kiel, dated November 7, informs us of the elements and 
ephemeris of this comet for the ensuing weck, computed by 
Prof. H. Kreutz from observations made on November 2, 4, and 
6. These are as follows :— 
T = 1897 February 6°819 Berlin Mean Time. 
o= 164 58:8 
8 = 85 10°2 > 1896'0. 
z= 146 54!) 
log g = 0°06722 
