540 
NATURE 
[SEPTEMBER 28, 1899 
mining engineers in South Africa. The courses of instruction 
are intended to prepare students for a diploma of mining 
engineer, or for the degrees of B.Sc. or M.Sc. in mining engineer- 
ing. Theoretical and practical instruction is given, under the 
direction of the principal, Mr. James G. Lawn, in mining, 
mechanical and electrical engineering, metallurgy, assaying, sur- 
veying and other subjects. Practical work is carried on in the 
mines and workshops of the De Beers Company, and also in 
various mines at Johannesburg. The time spent at Johannesburg 
is devoted to a special study of the cyanide process in all its 
developments, of the electrical machines and appliances at the 
mine where the student is working, of the methods of assaying 
and surveying and of the economics of mining on the Rand, 
A thorough training for mining engineers is thus provided in 
connection with the school, the course of work described in the 
prospectus being of a very satisfactory character. 
Tue London Technical Education Board have arranged 
several advanced evening science courses in connection with 
King’s and University Colleges, to commence next month. 
The courses of instruction will afford an opportunity to students 
who can study only in the evenings to obtain instruction in 
well-equipped University laboratories, and will make available 
to evening students the same advantages as are enjoyed by 
University day students, but they are only intended for those 
who are practically engaged during the day in some trade, 
business or occupation.—A course of twenty lectures on civil 
engineering will be given by Prof. Robinson, at King’s 
College, on Mondays, from 7 to 9, commencing on Monday, 
October 9. Part of the time will be spent in working out 
engineering calculations by graphical methods.—A course 
of about twenty demonstrations will be given by Prof. Capper 
and Mr. H. M. Waynford, at King’s College, on Thursday 
evenings, 7 to 9, upen ‘‘ Steam and Gas Engines and Generai 
Laboratory Work,” commencing October 12. The latter 
portion of each evening will be devoted to experimental and 
practical work in the engineering laboratory in illustration of 
.the lectures. —A course of about twenty lectures*on mechanical 
-engineering will be given by Prof. Hudson Beare, at University 
«College, on Friday evenings from 7.30-9.30, commencing 
‘Friday, October 13.—A special course of lectures on alternating 
currents will be given by Prof. Wilson, at King’s College, on 
Monday evenings, at 6.30 p.m., beginning October 9.—The 
following courses have been arranged to be held under the 
direction of Prof. Ramsay, at University College. In both of 
these courses the work will be oégéna/. (a) A course of 
twelve lectures on sewage and its purification, by Dr. Samuel 
Rideal, on Mondays, at 5.30 p.m., commencing November 6. 
- (4) A course of lectures on spectroscopy and spectrography 
will be delivered by Mr. E. C. C. Baly. 
SCIENTIFIC SERIAL. 
Wiedemann’s Annalen der Physik und Chemze, No. 8.— 
Limits of the solid state, by G. Tammann. Experiments on a 
mumber of organic bodies show that even when the heat of 
fusion is very nearly or accurately zero, the difference between 
the specific volumes of the liquid and the crystals is consider- 
able. —Magnetic properties of hematite, by A. Abt. The maxi- 
mum magnetic moments of three equal prisms, of pyrrhotite, 
hematite and magnetite respectively, were found to be in the 
ratio of I to 2°356 to 3'237. Pyrrhotite shows the smallest 
magnetisation in comparison with its percentage of metallic 
iron. —The blue steam-jet, by A. Bock. <A sky-blue colour is 
imparted toa steam-jet by sending through it a current of air 
saturated with hydrochloric acid. The jet, as regards colour, 
polarisation and diffraction, shows a close analogy with the 
atmosphere.—Resistance of alloys, by R. H. Weber. To 
measure the resistance of brittle alloys, like those of zinc and 
copper in which the zinc preponderates, the author employs the 
alloy in the form of thick plates or cylinders. A magnetic 
needle is made to vibrate over the plate, and its logarithmic 
decrement is directly proportional to the conductivity of the 
alloy. The method has the further advantage that the substance 
need not be exposed to much mechanical working, such as is 
involved in wire-drawing.—Work consumed .in a spark gap, by 
E. Riecke. In a 40-plate Toepler machine, the work consumed 
with a gap of 2 cm. is 1°64 watts per turn, and with a gap of 
6 cm. it is 3°27 watts. A turther increase of the width of gap 
diminishes the work of the spark.—Pressure in the spark, by 
NO. 1501, VOI. 00 
E. Haschek and H. Mache. By noting the increase of pres- 
sure in a vacuum tube on sparking, and the volume of the spark 
itself, the authors arrive at an estimate of the pressure within 
the spark. It is of the order of fifty atmospheres.—Potential 
gradient at the anode, by C. A. Skinner. The drop of 
potential from the anode to the adjoining gas during a 
low discharge is about 20 volts. This increase is to about 
40 volts within a distance of a few millimetres from the 
anode ; but there is no potential gradient within the thin lumi- 
nous layer immediately adjoining the anode. The greater the 
drop of potential at the anode, the less is the potential gradient 
in the anode light.—A radio-active substance, by E. de Haén. 
By extraction from a large quantity of uranium ore, the author 
has obtained substances which possess the properties ascribed 
to “fradium” in an extraordinary degree. One preparation 
exhibits all the properties of Becquerel radiation, and, in ad- 
dition, possesses the property of being strongly luminous. This 
luminosity is rapidly impaired by moisture, and can only be 
restored by melting the substance in the oxyhydrogen blow- 
pipe. 
SOCIETIES AND ACADEMIES. 
PAaRIs. 
Academy of Sciences, September 18.—M. Maurice Lévy 
in the chair.—Variations of volume in Portland cement resulting 
from setting and hygrometric state, by M. Considere. The 
expansions of cement prisms immersed in water were studied 
for a period of over two months, comparisons being made 
between loaded and unloaded prisms. The expansions in- 
creased very regularly, and were much less with a mixture of 
cement and sand than with pure cement. Owing to this 
gradual expansion, metal plates holding cement under water 
may be submitted to much greater stresses than has been 
hitherto supposed.—On the development of a holomorphic 
function at the interior of a contour in a series of polynomials, 
by M. Renaux.—On some experiments designed to confirm 
Ampere’s hypothesis relating to the direction of the elementary 
electromagnetic action, by M. W. de Nikolaiéve.— On Egyptian 
pottery, by M. H. Le Chatelier. Analyses of five different 
specimens of Egyptian pottery are given, together with a repro- 
duction of the microscopic appearance of two of them. 
CONTENTS. PAGE 
Incandescent Gas Lighting : a ss) ecm eZ, 
An American Text-book of Geometry. By G. 
: 517 
Our Book Shelf :— 
Hall and Stevens: ‘fAn Elementary Course o 
Mathematics” . 518 
Carvell : ‘* Carvell’s Nursery Handbook, with Hints” 518 
Shelley: ‘‘ Chats about the Microscope” ..... 518 
Letters to the Editor :— 
The Life ofa Star—Dr. T.J.J. See ... 519 
Remarkable Lightning Flashes. (Z//ustrated. jee! iE, 
Stromeyer; Prof. Henry Stroud; T. W. 
Backhouse ; BH Glew = . 520 
Sedge- Warblers Seizing Butterflies. Oswald H. 
Latter . . 520 
Explosion of /Sianiaienn Todide: —_Prof. P, ie Narasu 520 
The Dover Meeting of the British Association . . 521 
Section E.—Geography.—Opening Address by Sir 
John Murray, K.C.B., F.R.S., President of the 
Section 521 
Section G.—Mechanical ‘Science. — Opening Address 
by Sir William White, K.C.B., F.R.S., 
President offffe Sectionween >; =. < . cales Sue om 
Notes . 5 3) I 8 cote SSS 
Our Astronomical Column :— 
New Algol Variable in ee es «+e SoS 
Stellar Parallax eae CREE Oo >. 6 0) SRS 
Precession Tables. . . . . > Let aS OS: 
Longitude from Moon Culminations PL: =» «| 538 
The Royal Photographic Society’s Exhibition. By 
Cj; Re hoe. SS) 
University and Educational ‘Intelligence Ra Once fo, | SSK) 
Scientific Serial ... o 0 8 (POOR enw! So 549 
Societies and Academies > Gy 0 Drees c 549 
