60 NATURE 
[JANUARY 13, 1923 


from Annelids. Hence if the Apodide (and all other 
Crustacea) arose from Trilobites possessing biramous 
limbs, their own foliaceous appendages must be 
presumed to be derived from the biramous type, not- 
withstanding the similarity of their structure to the 
foliaceous uniramous parapodia of some Annelids. 
It is possible that the bilobed type of parapodium 
possessed by many Annelids may have given rise to 
the biramous Crustacean limb. On the other hand 
there is the objection felt by a few that the descent 
of the Apodide and other Crustacea from an ancestral 
group of Trilobites does not necessarily follow from 
the fact that Trilobites are the earliest known 
Crustacea. The Apodide themselves have many 
Structural affinities with Annelids. Thus it is con- 
ceivable that the Crustacean-Annelid may have pro- 
duced divergent branches of which the Trilobites 
(biramous-limbed) represent one, and the Apodide 
(foliaceous-limbed) the other. This view, however, 
is not regarded with favour by the chief authorities. 
Ar the sitting of the French Academy of Sciences 
held on October 23, 1922, a note was presented by 
MM. Constantin, Joessel, and Daloz ‘ concerning 
a boat which travels against the wind while using 
the wind itself for motive power.” An article on 
the same topic, entitled ‘‘Un bateau paradoxal,” 
appears in La Nature of November 11. An ordinary 
sailing- boat cannot use the wind for directions 
which are too near that directly opposite to the 
wind, and it was long ago suggested that if an arrange- 

ment like the sails of a windmill were substituted 
for ordinary sails, the boat could travel even against 
the wind. Napoleon was urged to use this as a means 
of surprising the British fleet. Scientific work on 
the idea was initiated in 1901 by Constantin, who ~ 
constructed a model car on wheels which advanced 
against a current of air blown on it. The publication 
of Drzwiecki’s theory of propellers in 1909 encouraged 
Constantin to proceed further. He attracted the 
attention and approval of many French men of 
science, and a syndicate was formed for the develop- 
ment of the method, but the war interrupted the work. 
In 1917 work was resumed, and since then the idea 
has been applied successfully. Joessel (son of the 
well-known investigator in aerodynamics) put an 
air-secrew—like the sails of a windmill—of 5 metres 
diameter into a 2-ton sloop, La Drésinette, connected 
with a marine propeller of 60 cm. diameter, and success- 
ful journeys were made on the Erdre, near Nantes, 
and on the Loire. This was in 1918. Later on a 
g-metre air-screw was installed in the 5-ton boat Bois 
Rosé, connected with a marine propeller of 105 cm. 
diameter, and on September 15, 1922, this boat sailed 
successfully on the Seine, between Saint Cloud and 
Sévres, in all winds and against the wind, without 
causing any derangement in the ordinary traffic. 
It was estimated that the speed was 2 metres per 
second against a wind of 7 metres per second. The 
investigations were conducted with the help of the 
French Direction des recherches scientifiques et im- 
dustrielles et des inventions. 

Our Astronomical Column, 
THE PLaneT MeRcury.—This planet reaches its 
easterly elongation on January 13 and will be favour- 
yk placed for naked-eye observation at about that 
date. 
The best time to obtain a glimpse of the planet 
will be at about an hour after sunset, when it may 
be seen at a low altitude over the west-south-west 
horizon. The planet may be expected to be about 
as bright as a first magnitude star would appear in 
a similar position and involved in twilight. Mercury 
does not shine with the same steady light as some 
of the larger planets, but often exhibits a sparkling 
fitful lustre. 
Being rarely visible owing to its proximity to the 
sun, it is necessary for intending observers to look for 
the planet at special periods like the present, when 
its apparent elongations from the sun enable it to be 
perceived with the unaided eye. 
THE JANUARY METEORS,—A brilliant full moon and 
passing clouds somewhat interfered with observation 
of this event. The maximum display was expected 
on January 3, and Mr. W. F. Denning writes that at 
Bristol fine meteors were visible occasionally, and 
indications were that had the conditions been favour- 
able, the shower would have been fairly conspicuous 
and plentiful. 
At Stowmarket, Miss A. Grace Cookand Mr. J. Pa: 
Prentice obtained independent observations on the 
night mentioned, and remarked some fine meteors 
from the usual point of radiation at 232° +52°. 
The sky was not watched after midnight and the 
maximum seemed to have been attained in the 
earlier part of the evening. Miss Cook recorded 
bright meteors from the special shower of Quadrantids 
NO. 2776, VOL. 111] 

at 65 58™, 82 ro™, 82 43™ and 10h 18™, and there were 
others of about mag.1. At 9" 36™ there was a fireball 
from the direction of Aquarius. 
On the night of January 4, the shower of Quadrantids 
seemed to have become nearly extinct. At 8h 48™, 
however, Miss Cook witnessed the appearance of a 
remarkable stationary meteor. It was as bright as 
Venus, and shone for about 14 seconds with a motion- 
less aspect at the position 222°+77°. There is a 
known shower at this point in Ursa Minor and it 
corresponds with the point of radiation of Mechain- 
Tuttle's Comet on December 20. 
CoMING SOLAR Ec.ipsEs.—The eclipse of September 
10, 1923, will be total in California and Mexico. The 
sun’s altitude will be more than 60°, and the duration 
of totality 3} minutes. The weather prospects are 
very hopeful. There is little doubt that the Einstein 
problem will again be studied. Mr. F. Slocum (Asir. 
Journ. No, 809) gives a list of the stars within 2}° of 
the sun’s centre down to mag. 9:0. They are mostly 
faint, especially those nearer the sun, and it will need 
skilled photography to record them. It is proposed 
to photograph a check field, some 5° distant, on the 
same plates during totality, thus giving an independ- 
ent determination of scale value, and enabling the 
whole Einstein displacement to be utilised. Other- 
wise much of it is lost, only the differential shift being 
available. 
The succeeding totality, on January 24, 1925, 
crosses the north-eastern states. Four observatories 
—Vassar, Yale, Van Vlack, and Nantucket—enjoy 
total eclipse; its duration is 1} minutes, but the 
sun’s altitude is less than 20°. The star field is better 
than that of 1923 but not so good as 1919. 

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