326 
NATURE 
[JANUARY 31, 1907 
stopped and of being quickly started, either ahead or 
astern; (c) it must be capable of being promptly speeded 
to any desired point between full speed and dead slow, 
which latter speed ought not to be greater than one-quarter 
of the full speed; (d) it must be capable of working well, 
not only in smooth water, but in heavy weather in a sea- 
way in which the varying immersion of the propeller causes 
rapidly changing conditions .of resistance. In marine 
engines the revolutions are practically proportional to the 
speed of the ship, and as the vessel’s resistance increases 
much more rapidly than the speed, it follows that for a 
reduction of speed of revolution the mean effective pressure 
must be reduced much more than in proportion to the re- 
volutions. This is a much more difficult problem in marine 
engines, where no fly-wheel is practicable, than on land, 
where the use of a heavy fly-wheel permits the suppression 
of alternate fuel charges. 
A LITTLE essay of twenty-four pages has been published 
by M. Prosper de Lafitte on ‘“‘ The Magic Square of n 
with n Numbers.’’ By this is meant a square with n? 
spaces, containing the numbers from 1, 2, 3, . . n each 
repeated n times, in such a way that each row, each 
column, and each diagonal contains each number once. 
This is, of course, a slightly different problem from that 
of the ordinary magic square, which contains all the 
numbers from 1 up to n*; and the author’s claim to have 
produced a paper calculated to instruct as well as to 
entertain the reader is well justified:’ Messrs. Gauthier- 
Villars, of Paris, are the publishers. 
In the Atti dei Lincei, xv., 10, Dr. Pietro Macchia dis- 
cusses the relations between thermal conductivities at 
ordinary and at low temperatures. In determining the con- 
ductivity, observation is made of the distribution of tempera- 
ture in a rod subject to surface radiation, when the flow of 
heat has become steady. Even at moderate temperatures 
results based on Stefan’s law are shown to be better than 
those derived from Newton’s law of cooling. Thus for pure 
lead, the ratio of the conductivities deduced from Stefan’s 
law, for temperatures 18° and 100° respectively, works 
out at 1-016; Jager and Diesselhorst’s determinations, 
based on the consideration of non-stationary states, give 
1-015, while the assumption of Newton’s law gives 2-01. 
Messrs. A. E. Stary anp Co., of 19 Thavies Inn, 
Holborn Circus, E.C., have submitted for our inspection 
a pair of their new ‘‘ Nikos,” 8x, prismatic binoculars, 
which. are sold at the low price of 61. 10s. The instru- 
ment is beautifully finished in Russia leather, and is of 
a very compact, light, and handy form, whilst its perform- 
ance optically satisfied the critical tests to which we 
subjected the pair examined. There is a common focussing 
screw for both eye-pieces, one of which is fitted, how- 
ever, with a separate arrangement, and the bending bar 
is adjustable to the distance between the observer’s eyes by 
simply bending it the required amount. Both the special 
focussing arrangement and the bending bar are provided 
with scales, so that the habitual user may adjust the 
glasses before using them without having to make a series 
of trials each time. A pair of studs projecting from the 
object-glass end of the glasses enables the latter to stand 
flat on any horizontal surface. 
Tue issue of ‘‘ Hazell’s Annual ’’ for 1907 is now avail- 
able. The alphabetical arrangement of this cyclopzedic 
record reduces the trouble of reference to a minimum, and 
the comprehensive character of the contents makes the 
volume of wide interest. 
NO. 1944, VOL. 75 | 
A THIRD edition of ‘‘’The Mechanism of Weaving,’ by 
Mr. Thomas W. Fox, of the Manchester Municipal School 
of Technology, has been published by Messrs. Macmillan 
and Co., Ltd. The opportunity has been taken to revise. 
the text carefully, to add matter relating to recent develop- 
ments in weaving, to introduce numerous new _ illustra- 
tions, and generally to enhance the value of the work from 
the points of view of teachers, students, and men actively 
engaged in the cotton industry. 
Tue thirteenth edition of ‘* Practical Sanitation,’’ by Dr. 
George Reid, has been published by Messrs. C. Griffin and 
Co., Ltd. The appendix on sanitary law, by Mr. H. 
Manley, has been entirely re-written, and other parts of 
the work have undergone detailed revision, particularly the 
chapter which deals with sewage disposal. The work 
provides medical officers of health, sanitary inspectors and 
others interested in sanitation with a comprehensive survey 
of the practical and scientific aspects of sanitary science. 
We have received a copy of the first number of the 
African Monthly, a magazine to be devoted to literature, 
history, exploration, science, and art, as well as fiction. 
The new periodical is published by the African Book 
Company, Ltd., of Grahamstown, Cape Colony, and its 
price is 1s. The contents of the first issue are varied and 
interesting; scientific subjects are represented by two 
articles, ‘‘ The Bantu in the Tenth Century. As described 
in Extracts from the ‘ Golden Meadows’ of Al Mas’udy,”’ 
by Mr. W. Hammond Tooke, and ‘‘ Merino Sheep Breed- 
ing in Australia,’’ by Mr. R. H. Harrowell. The maga- 
zine may be obtained in this country from Messrs. Wm. 
Dawson and Sons, Ltd., Cannon House, Breams Buildings, 
London, E.C. 
OUR ASTRONOMICAL COLUMN. 
Tue Recent Torat EcLirsE OF THE SuN.—A telegram 
received by Prof. Kreutz from Prof. R. Schorr at 
Dschisak, in the province of Samarkand, states that during 
the whole time that the sun was eclipsed on January 14 
the sky was totally obscured, and snow fell heavily. Only 
meteorological and some photometric observations were 
possible (Astronomische Nachrichten, No. 4150). 
Herr Archenhold has received a similar message from 
another observer at Samarkand, whilst the Moscow 
observers are reported to have obtained no results even 
in the meteorological and photometric programme (Das 
Weltall, January 15). 
Tue Sorar Rapration.—The depression of the ‘‘ solar 
radiation ’’ during 1903, as observed at Warsaw, is dealt 
with in a paper communicated to the Bulletin météor- 
ologique du Département de l'Hérault by M. Ladislas 
Gorezynski. The observations showed that between 
December, 1902, and February, 1904, the radiation was 
abnormally low as compared with the mean for the years 
1901-5. This phenomenon has previously been commented 
upon by various observers, and is supposed to have been 
due to the large amount of volcanic dust in our atmo- 
sphere. Two other abstracts from the same bulletin deal 
respectively with the variations of the intensity of the solar 
radiation with the height of the sun, and the amount of 
the insolation at Warsaw, Treurenberg, and Montpellier. 
¢ 
PHOTOGRAPHS OF GIACOBINI’S COMET (1905c).—The way 
in which a comet's tail develops as the comet approaches 
perihelion is beautifully shown by a series of photographs 
of Giacobini'’s 1905 comet which are published in Bulletin 
No. 25 of the Lowell Observatory. The series extends 
from December 14, 1905—-eight days after the comet’s dis- 
covery—when the object showed only a well-defined nucleus, 
to January 7, 1906, when three distinct tails are shown, 
the middle one extending to a distance of 10°. from the 
head. 
