Intelligence and Miscellaneous Articles. 559 



reach so far north as Eichmond. The presence of pervious beds of 

 the Xew Eed may possibly be found to compensate in some degree 

 for the absence of the Xeocomian as a source of water-supply. 



(3) The discussion of these facts throws some new light on the 

 problem of the existence of Coal-bearing strata at workable depths 

 under London. Small particles of anthracite were found in several 

 of the deeper bed3 at Eichmond, these being probably derived 

 from Coal-seams in the great Palaeozoic axis ; bat the presence of 

 Jurassic and Triassic strata shows tbat a greater thickness of strata 

 will probably have to be pierced in order to reach the coal than 

 was formerly supposed. 



The paper concludes with some note3 on the very interesting and 

 beautifully preserved fossils from the Great Oolite bed3 under 

 London. 



LXIY. Intelligence and Miscellaneous Articles. 



OBSERVATIONS OX EARTH CURRENTS IN LINES A KILOMETRE IN 

 LENGTH. AND THEIR COMPARISONS WITH MAGNETIC VARIA- 

 TIONS. BY H. WILD. 

 HP HE International Congress of Electricians which met in Paris 

 -*■ from the 16th to the 26th October, 1882, formulated the 

 following resolutions among others : — 



M It hopes tbat certain lines, even of small length, independent 

 of the general telegraph system of each country, will be ex- 

 clusively devoted to the investigation of earth current s.' v 



Thanks to the kindness of the Directorate of Russian Telegraphy, 

 the Meteorological and Magnetic Observatory of Paulo wsk has 

 already, since the month of August 1882, been in possession of two 

 submarine lines, each a kilometre in length, one being perpendi- 

 cular and the other parallel to the magnetic meridian. Each of these 

 lines is connected with an aperiodic galvanometer set up in the 

 underground pavilion for observing magnetic variations; so that 

 the readings of the scale may be made at the same time as those of 

 the variation instruments. The Observatory of Paulowsk was thus 

 in a position to realize the hope of the Congress ; and earth cur- 

 rents have been regularly observed in these two lines during the 

 period of the Polar Expedition (that is. from the 1st of September 

 1882 to the 1st of September 1883) three times a day. and on the 

 special days of observation every five minutes for twenty-four 

 hours. 



In a paper (Memoires de VAcad. imp. des Sc. de St. Petersbourg, 

 vol. xxxv. No. 12) I described in detail the method of observation 

 which I used in these researches. I particularly dwelt on the dif- 

 ficulty which arises in these short lines from the different electro- 

 motive force of the electrodes ; so that we must distinguish clearly 

 between the earth current properly so called, which bifurcates 

 in the lines by the electrodes for earth plates), and the currents 

 which are only due to the electrical difference of these plates. By 



