"Meditationis est perscrutari occulta; contemplationis est admirari perspicua. . . . . Admiratio generat quæstionem, quæstio investigationem, investigatio inventionem."-Hugo de S. Victore.

"Cur spirent venti, cur terra dehiscat,

Cur mare turgescat, pelago cur tantus amaror,
Cur caput obscura Phœbus ferrugine condat,
Quid toties diros cogat flagrare cometas;
Quid pariat nubes, veniant cur fulmina cœlo,
Quo micet igne Iris, superos quis conciat orbes
Tam vario motu."

J. B. Pinelli ad Mazonium.

CONTENTS OF VOL. XLVII.

(FOURTH SERIES.)

NUMBER CCCIX.-JANUARY 1874.

Mr. J. Y. Buchanan on an Apparatus for Gas-analysis.
(With a Plate.)..

M. H. Herwig on the Disintegration of the Electrodes in the
Galvanic Arc of Light

Prof. Challis's Theory of the Source of Terrestrial Magnetism.
Mr. R. S. Brough on Wheatstone's Bridge...
Prof. Challis's further Discussion of the Analytical Principles
of Hydrodynamics, in Reply to Mr. Moon..

M. A. F. Sundell on the Electromotive and Thermoelectric
Forces of some Metallic Alloys in contact with Copper....
Mr. S. Roberts on a simple Condensing Collector for Fric-
tional Electrical Machines

Page

1

6

14

22

25

28

49

Prof. W. F. Barrett on the Molecular Changes that accompany the Magnetization of Iron, Nickel, and Cobalt

51

Notices respecting New Books:

56

Mr. J. M. Wilson's Elementary Geometry.

Proceedings of the Royal Society:

Dr. J. H. Gladstone and Mr. A. Tribe on an Air-Battery. 61
Mr. O. Reynolds on the Condensation of a Mixture of
Air and Steam upon Cold Surfaces

Proceedings of the Geological Society :

Mr. S. Sharp on the Oolites of Northamptonshire.-
Part II.

67

74

On some Phenomena of Illumination, by A. Lallemand
On a Process for verifying the Nodes in a Sounding Pipe, by
M. Bourbouze

77

80

NUMBER CCCX.-FEBRUARY.

Lord Rayleigh on the Manufacture and Theory of Diffractiongratings...

81

Mr. O. Heaviside on Wheatstone's Bridge

93

Mr. J. Croll on the Physical Cause of Ocean-currents
Prof. W. H. Miller on Quartz, Ice, and Karstenite

94

122

Prof. E. C. Pickering's Measurements of the Polarization of the Light reflected by the Sky and by one or more Plates of Glass

127

Page

Mr. R. Moon's Remarks on the Analytical Principles of Hydrodynamics, in Reply to Professor Challis

143

Dr. Helmholtz on Galvanic Polarization in Liquids free from
Gas

145

Notices respecting New Books:

Mr. W. T. Pierce's Treatise on Practical Solid or Descrip-
tive Geometry: embracing Orthographic Projection and
Perspective or Radial Projection..

153

Prof. M. Yarnall's Catalogue of Stars observed at the
United States Naval Observatory during the years 1845
to 1871 ..

155

155

On a new Determination of the Mechanical Equivalent of Heat,
by H. Serrano y Fatigati....
On the Expansibility of Ebonite by Heat, by F. Kohlrausch.. 156
On the Discharge of Electrified Conductors, by J. Moutier 157

NUMBER CCCXI.-MARCH.

The Earl of Rosse on the Electric Resistance of Selenium .. 161 Mr. J. A. Phillips on the Composition of certain Mine Waters. 164 Mr. J. Croll on the Physical Cause of Ocean-currents. (With

a Plate.)...

168

.. 190

M. H. Herwig on the Number and Weight of the Molecules
of Ether contained in Electric Conductors
Lord Rayleigh on the Manufacture and Theory of Diffraction-
gratings.

193

M. J. L. Soret on some Phenomena of Polarization by Diffusion of Light..

205

M. A. Terquem on the Transformation of the Vibroscope into a Tonometer, and its employment for the Determination of the Absolute Number of Vibrations

212

Notices respecting New Books :—

The Rev. S. Hawtrey's Introduction to the Elements of
Euclid

215

Proceedings of the Royal Society:

Lieut. Sale on the Action of Light on the Electrical Re-
sistance of Selenium

216

Mr. D. M'Kichan's Determination of the Number of
Electrostatic Units in the Electromagnetic Unit
Messrs. Stewart and Tait on the Heating of a Disk by
rapid Rotation in vacuo.

218

219

Mr. F. Chambers on the Diurnal Variations of the Wind
and Barometric Pressure at Bombay

228

Proceedings of the Geological Society :—

Dr. J. Bryce on the Jurassic Rocks of Skye and Raasay. 229
Mr. D. Mackintosh on the more remarkable Boulders of
the North-west of England and the Welsh Borders .. 230

Mr. T. Davidson on some Brachiopoda collected by Mr.
Judd from the Jurassic Deposits of the East Coast of
Scotland..

Page

230

Prof. D. T. Ansted on Solfataras and deposits of Sulphur
at Kalamaki

230

Mr. J. Lucas on the Origin of Clay-Ironstone

231

Dr. Dawson on Leptophloum rhombicum and Lepidoden-
dron gaspianum

231

Capt. F. W. Hutton on the younger formations of New
Zealand

232

Mr. W. Carruthers on the Tree Ferns of the Coal-mea

sures

233

Mr. A. H. Schindler on the Geology of Kazirùn

233

The Rev. T. G. Bonney on the Lakes of the North-eastern
Alps

234

Signor B. Gastaldi on the Effects of Glacier-erosion in
Alpine Valleys

235

On the Limits of the effective Power of Microscopes, by Pro-
fessor Helmholtz ...
Experimental Researches on Newton's Coloured Rings, by P.
Desains

236

236

On extraordinary developments of Light in the grinding of hard Stones, by Dr. Jacob Nöggerath

237

NUMBER CCCXII.―APRIL.

Prof. J. P. Cooke on the Vermiculites; their Crystallographic and Chemical Relations to the Micas; together with a discussion of the Cause of the Variation of the Optical Angle in these Minerals (With a Plate.)

241

M. H. Vogel on the Sensibility to Light of Bromide of Silver
with respect to the so-called Chemically Inert Colours
Prof. Challis on the Effects produced by Fog and Vapour in
the Atmosphere on the Intensity of Sound

273

277

M. G. Lippmann on the Connexion between Capillary and
Electrical Phenomena. (With a Plate.)

281

Mr. R. Moon on the Measure of Work in the Theory of Energy. 291
M. F. Kohlrausch on the Determination of the Absolute Value
of the Siemens Mercury Unit of Electrical Resistance .... 294
Proceedings of the Royal Society:-

Sir B. C. Brodie on the Electric Decomposition of Car-
bonic-Acid Gas ..

309

Messrs. Lockyer and Roberts on the Quantitative Ana-
lysis of certain Alloys by means of the Spectroscope.. 311
Mr. J. A. Broun on the Period of Hemispherical Excess
of Sun-spots, and the 26-day Period of Terrestrial
Magnetism..

311