210 
ME. C. V. WALKEE ON MAGNETIC CALMS AND EAETH-CLEEENTS. 
heads, — one semi-barb indicating column 1 ; two, column 2 ; three, column 3. The 
arrow-heads pointing upwards all apply to “ up ” currents u ; those pointing down- 
wards, to “ down ” currents d. The dotted portion of the circumference of the circle is 
the arc of the horizon, within which the resultant is to be found. The degrees are 
given reckoned from the north, eastward round the cu’cle. Fig. 10 represents the IS.E. 
normal, or u, d, u, in Tables XIII. and XV. ; fig. II the S.W. normal, or d, u, d. 
From these Tables it appears that the prevailing currents, or those of most frequency, 
are from the N.E. or S.W.; this as well in calm periods as in periods of magnetic storms. 
In the absence of long-continued and consecutive observations, it is not easy to form an 
opinion as to whether the N.E. or S.W. currents prevail more or less at one part of the 
day than at another ; or to what extent, if at all, the directions or alternations are 
influenced by local meteorological changes or conditions. In ‘ Les Archives des Sciences 
Physiques,’ vol. xi. pp. 110-136, is a memoir by Father Secchi, “On the Connexion of 
Meteorological Phenomena and Variations of the Intensity of Terrestrial Magnetism,” 
in which he expresses very strongly his opinion that every rupture of meteorological 
equilibrium produces a rupture of electrical equilibrium, which can only be re-estabhshed 
by means of a current which discharges itself from place to place, which current cannot 
fail to act upon the magnetometers. Here is a wide field for research. Although I am 
not engaged in investigating the origin of the currents, I cannot avoid expressing my 
opinion that the value of existing currents, if not their direction (I speak locally), may 
be more or less influenced by meteorological changes, especially cloud, sunshine, or tem- 
perature. The currents at calm periods are at best but feeble. The resistances of the 
various parts of the telegraph wire through which they pass vary with the varying tem- 
peratures, so that it is quite reasonable to expect that, even when no change is taking 
place in the absolute value of the current travelling in the earth, the needle of the 
galvanometer may move forward or backward according as sunshine or cloud, heat or 
cold prevail here or there in the district under examination. This opinion is sanctioned 
in some degree by the result of some night observations made on October 28 — 29. My 
original observations were almost wholly made by day. On the night in question obser- 
vations were made every ten minutes from 10. 10 p.m. to 6.50 a.m, Huilng this period 
there was evidently an excess of S.W. currents ; the proportion of u, d, u to d, u, d currents 
was 1 : 2‘7, whereas the day proportion for the month was 3’7 : 2’7. Also fifteen out of 
the twenty-five d, d, d currents were collected during the night ; in fact there were only 
ten u, d, u currents in the whole fifty-six night observations. From 11.40 p.m. to 5.40 a.m. 
the London-Dover wme collected a continuous down d current, varying more or less in 
intensity; from 5.40 to 6.30 a.m., the current was too feeble to be appreciated; at 6.40 
it was found in the reverse direction u, and was so when the observations were inter- 
rupted at 7.47. — These remarks in passing. 
There is no consistency in the relations between two derived currents collected at the 
same time from the same earth-drift of electricity : this may be in great measure due, 
as I have hinted, to local meteorological interference, if not to the absolute difierences 
