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“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 Phæbus ferrugine condat,
Quid toties diros cogat flagrare cometas;
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Tam vario motu.”

J. B. Pinelli ad Mazonium.

CONTENTS OF VOL. XLVII.

(FOURTH SERIES.)

NUMBER CCCIX.--JANUARY 1874.

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

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

6 Prof. Challis's Theory of the Source of Terrestrial Magnetism. 14 Mr. R. S. Brough on Wheatstone's Bridge..

22 Prof. Challis's further Discussion of the Analytical Principles of Hydrodynamics, in Reply to Mr. Moon

25 M. A. F. Sundell on the Electromotive and Thermoelectric

Forces of some Metallic Alloys in contact with Copper... 28 Mr. S. Roberts on a simple Condensing Collector for Frictional Electrical Machines

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

51 Notices respecting New Books :Mr. J. M. Wilson's Elementary Geometry.

56 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 .

67 Proceedings of the Geological Society Mr. 8. Sharp on the Oolites of Northamptonshire.

74 On some Phenomena of Illumination, by A. Lallemand 77 On a Process for verifying the Nodes in a Sounding Pipe, by M. Bourbouze

80

Part II. ...

NUMBER CCCX.–FEBRUARY.
Lord Rayleigh on the Manufacture and Theory of Diffraction-

gratings.....
Mr. O. Heaviside on Wheatstone's Bridge ...
Mr. J. Croll on the Physical Cause of Ocean-currents
Prof. W. H, Miller on Quartz, Ice, and Karstenite
Prof. E. C. Pickering's Measurements of the Polarization of
the Light reflected by the Sky
and by one or more Plates of

127

81 93 94 122

Glass