206 
IN connection with the abnormally cold weather which has 
prevailed over the British Isles, and to a great extent over 
Western Europe also, since the closing days of April, con- 
siderable interest attaches to the temperature of the surface 
water of the Atlantic during the month of April. The mean 
results, derived from a total of 4150 observations, are given on 
the pilot chart for June, just issued by the Meteorological 
Office. There appears to have been an almost complete absence 
of ice about the banks of Newfoundland, a fact which is 
emphasised by the sea water of that region being warmer than 
usual, the excess ranging upwards to as much as 6° in places. 
Westward of the thirty-fifth meridian, from 30° to 35° N., the 
temperature was also rather above the normal, but from the 
coast of Virginia eastward between these relatively warm 
patches, along what may be described, roughly, as the Gulf 
Stream course, there was a deficiency of temperature right 
across the ocean to our coasts, the eastern half of the Atlantic 
being below the average. Northward of the fiftieth parallel it 
would appear that there are no normals available for com- 
parison with the present series, which is unfortunate, as the 
condition of the sea immediately to the west of our islands, 
between the Fastnet and Iceland, probably exercises an appre- 
ciable influence on our climate. Down to June 16, when the 
pilot chart went to press, there were still no ice reports of any 
importance on the banks, the latest being May 8, a piece of 
ice 4 feet square, one of May 5 relating to bergs stranded on 
the Newfoundland coast, north of Cape Race. The strait of 
Belle Isle was clear, but floes were drifting down the Labrador 
coast, so that steamers could not approach the strait from 
seaward. Iceland reports show that there has been a good deal 
of ice off the north-western part of the island. 
THE result of an investigation by Mr. Maxwell Tall relative 
to the mean maximum temperature and the rainfall of Jamaica 
and sunspot frequency has recently been published officially 
at Jamaica, and has already been mentioned in these 
columns (p. 159). The temperature observations, a full 
account of which he gives in the paper, extend over the 
years 1881 to 1898, and to eliminate minor irregularities Mr. 
Hall employs for the yearly value the mean of the year and 
the means of the year each side of this middle year ; thus, 
to take an example, the value for 1885 is the mean for the 
three years 1884, 1885 and 1886. The temperature variations 
found in this manner, when compared with the variation in the 
spotted area of the sun’s surface, bring out a close relationship 
between these two phenomena. Thus it is observed that the tem- 
perature is ata maximum at sunspot minimum and vice versd, 
and that this variation amounts to about 2°F. With regard to 
the variation of rainfall as deduced from a discussion of the 
yearly means of rainfall, Mr. Maxwell Hall has previously shown 
(NATURE, vol. xlix. p. 399) that up to the year 1887 there was 
a general resemblance between the sunspot curve and that of 
rainfall, the maxima and minima of the rainfall variations cor- 
responding approximately with those of the curve representing 
the sun’s spotted area, but there were certain irregularities which 
suggested that the old view that there was most rain at the maxi- 
mum and least at the minimum of the eleven-year curve was 
only approximately true. The further discussion of the rainfall 
observations up to the year 1899 shows, however, that this ap- 
parent law breaks down completely. When in 1889 and 1890 
the rainfall curve should have been at a minimum, in reality it 
showed a subsidiary maximum, while also when at the sunspot 
maximum of 1893-4 the rainfall should have been excessive, it 
was conspicuous by a great deficiency. 
THE important aid that photography can render to the surveyor 
has recently been well illustrated by a paper read before the 
Institution of Mining Engineers by Mr. Arthur O. Wheeler, 
NO. 1704, VOL. 66] 
NATURE 
[JUNE 26, 1902 
attached to the staff of the Canadian Topographical Survey. 
In this paper we have the actual experience of one who has 
been much engaged in practical surveying, and his notes having 
reference to the selection of stations and to the photographic 
processes necessary in the field are as valuable as those which 
deal with the after manipulation of the photographic enlarge - 
ments and the production of the contour maps. The applica- 
tion of the photographic method is based on the consideration of 
the triangle, the angles at the base of which are formed by lines 
drawn from the two known stations, at which the perspective 
view of the country has been obtained in the camera, to the 
point which is to be projected, and which may be considered 
the apex of the triangle. Accuracy demands that the triangle 
should be well conditioned, and reaches its highest value when 
the angle at the apex approaches a right angle. ‘There will be 
difficulties connected with the selection of suitable stations, 
difficulties in the identification of orientation points, which Mr. 
Wheeler makes no attempt to minimise, but a peculiar feature 
of the method is that it is best adapted to a country where the 
actual measurement in the field is tedious or impossible. It 
was pointed out in the discussion of Mr. Wheeler’s paper that 
the method did not offer great advantages in a country of gentle 
slopes and rounded outlines, with relatively small differences in 
elevation, because of the uncertainty of locating the points on 
different photographs. But when the country possesses no in- 
convenient features, other methods are easy of application. 
Moreover, it was urged that the plotting of the points is more 
laborious than in the older methods of surveying. Mechanical 
devices based on the theory of perspective can do much to 
shorten the office work of plotting, and in any case this delay 
and expense are more than compensated by the rapidity of the 
field work and the employment of a smaller number of assistants 
required to remove obstacles in an untravelled country. The 
method has been employed practically in Canada, where the 
Topographical Survey has been carried into regions the severe 
climate of which renders it desirable to shorten as far as 
possible outdoor operations. 
. A CONVENIENT form of rectifier and interrupter for use with 
alternating currents is described by Dr. Guilleminot in the 
Archives a’Electricité Médicale for May. The current to 
be used is led through a vibrating reed, which carries at its free 
end a contact dipping in and out of a mercury cup. The reed 
is placed between the poles of a permanent magnet and is 
magnetised by a coil of wire which surrounds it; the coil is con- 
nected (in series with self-induction and resistance) as a shunt 
to the main circuit. A damping arrangement is also attached 
to the reed. The reed vibrates in synchronism with the alter- 
nating current, and as the contact only dips into the mercury 
when the reed is deflected downwards, the main circuit is 
synchronously opened and closed, thus converting the alter- 
nating into an intermittent direct current. The great advantage 
of the apparatus is the ease with which it may be adjusted ; the 
mercury cup can be raised or lowered, thus regulating the time 
of closed circuit; the length of free reed can be varied, and the 
phase of the vibration relative to that of the alternating supply 
can be altered by varying the self-induction in series with the 
exciting coil. It is thus possible to open the circuit always at 
the most suitable point of the wave—which depends, of course, 
on the purpose for which the current is being used. The 
apparatus, which is said to give excellent results in Xtray work, 
is the invention of Prof. Villard, and is made by M. Chabaud. 
THE Zeitschrift fiir Elektrochemie for May 8 contains an 
interesting article by Dr. A. Ludwig upon the fusion of carbon, 
After referring to Moissan's classical work on this subject, and 
to the famous French chemist’s production of diamonds in the 
electric furnace, the author gives details of his own work. 
