Terrestrial Masmetism . 
BY PROF. RICHARD OWEN, INDIANA STATE 
UNIVERSITY, BLOOMINGTON, IND. 
Since the statement of facts on this and 
collateral subjects, in a former number of 
the Yalley Naturalist, daily observations 
with the galvanometer have been continued: 
all corroborating the results therein given, 
with one exception. It may be well briefly to 
restate the general results and then give the 
exception. 
1. In this part of Indiana, and probably 
all through the valley of the Mississippi, 
there are so-called currents of electricity in 
the earth's crust, near the surface, and, 
doubtless also at greater depths, flowing from 
east to west, due probably to the greater 
heat at a given moment at points east of any 
latitude, when compared with points west, 
because as the earth revolves from west to 
to east on its axis, the eastern localities 
sooner receive the warning rays of the sun. 
2. We have also currents running from the 
southerly portion of our continent, to the 
more northerly, due to the thermal differ- 
ence between tropical or sub -tropical and 
N. temperate or Arctic regions. These cur- 
rents from the south, so far as observed in 
Indiana, give nearly twice as much deflection 
of the galvanometer, as the currents from 
the east; consequently the mean resultant 
would be currents from somewhere between 
S. S. E. and S. E. treading between N. E. 
and N. N. E. 
3. It was mentioned in some communica- 
tions that the needle had sometimes refused 
to settle when the wires to the galvanometer 
came from rods which ranged from each 
other in certain points of the compass. In 
several instances the direction of the storms, 
as detailed in various journals (such as the 
Iowa storm of May 23d last and the Missouri 
storm of June 1st), coincided or nearly so 
with the record on those days giving the cur- 
rent in the range of some of the iron rods 
which showed electrical or magnetic storms 
in the crust of the earth. Usually on those 
days the electrical disturbance in the at- 
mosphere was indicated by the needle oscil- 
lating and not inclining to settle, but when 
it did for a moment, the deflection was more 
than double the ordinary record. 
4. It was formally stated that, so far as ex- 
periments had then tested, the facts, when 
one wire connected with some metal in the 
earth, the other with some metal above 
ground, say stove, lightning rod, &c, the 
curreut was from the atmosphere to the 
earth. 
The exception above alluded to, is found, 
provided the lightning rod is short, as when 
attached to a one or two story house, and 
when it runs six or eight feet into the ground, 
then the current may sometimes blow from 
the tank or scrap iron reservoir of metal to 
the lightning rod, instead of the contrary, as 
always occurs when one wire connects with 
the college lightning rod, or that from the 
Court House, where instead of being only 
about 30 or 10 feet high, the rod extends 
from 75 to over 100 feet into the air. 
5. To illustrate these currents and to show 
their effect in varying the needles from the 
geographical north, we may use a globe, al- 
though a block of wood or a simple stick 
with an upward curve may serve to illustrate 
the phenomena of declination and inclination 
under the following conditions. Place In a 
direction from S. S. E. to N. N. W. on the 
globe, block or stick, which should stand 
north of you, many coils of iresulated wire, 
wound as you face them, from right up and 
over to left, in other words contrary to the 
motion made by the hands of a watch, being 
careful to clamp to the positive poles the 
wire which starts from your right, while the 
wire which ends on your left is attached to 
the binding screw of the negative pole. Then 
operate your battery and test for variation, 
&c, with a delicate magnetic needle held in 
your hand by means of a cork, having a sew- 
ing needle thrust through the cork, as a pivot 
for the magnet. Now if your stick supports 
the coil high enough from the table, you can 
carry the magnetic needle all around the 
coil and observe the results. Let the upper 
part of the coil represent the western Hem- 
isphere, the lower part the eastern Hemis- 
phere. You will find the American agonic 
line (an imaginary line connecting all the 
places in that part of the globe, where the 
needle points to the geographical north) run- 
ning from near the eastern middle of your 
coil in a N. N. W. direction both upward 
and downwaad, toward the magnetic north 
pole, where your needle will be reversed and 
point with its marked end to the interior of 
your coil. Another agonic line correspond- 
ing to the Asiatic, which starts through the 
western part of Australia, will be found in 
an imaginary irregular place, passing nearly 
vertically through the southwest part of your 
coil, somewhat parallel to the American 
northwest agonic place terminated by the 
rather irregular circle first described. On 
the upper part of the coil, between the 
American agonic on the east and the Asiatic 
agonic on the west, the variation will be 
found more or less to the east of north. Un- 
derneath the coil the needle will take the 
same direction which for a spectator, view- 
ing the coil from below, would give the more 
or less western variation observed through 
all but eastern Asia. The anomalies in east- 
ern Asia and near mid Pacific can perhaps 
be accounted for when we ascertain exactly 
how all the thermo-electrical currents run. 
Tropica] Africa may send currents as well in 
a north-easterly as in a north-westerly direc- 
tion, which would thus account for the cross- 
ing in western Africa of the variation lines. 
6. Thus the sun, besides being the main 
source for light and heat for our earth, seems 
by these thermal differences to be the imme- 
diate cause of electrical currents in the earth 
and hence remotely also the cause of Terres- 
trial Magnetism ; a fact apparently further 
proved by the diurnal and annual variations, 
as well as by the supposed modification of 
magnetic dip through greater or less proxi- 
mity of the sun to the earth. 
Look out for the September issue— No. 9, 
If you are not already a subscriber, subscribe 
before that time. 
Meteorological Report of the City of 
Oakland.,, California. 
BY J. B. TREMBLY, M. D., OAKLAND, CAL. 
Meteorological synopsis for the month of 
June, 1878. Observations taken at 7 A. M. 
and 2 and 9 p. m. Latitude 37° 48' 20" north. 
Longitude 120° 15' 20" west. Height above 
the sea 24 feet. 
BAROMETER. 
Mean barometer for the month 29.87 
Highest barometer, June 1, 7 p. m 30.09 
Lowest " " 12,7 a.m.... 29.75 
Monthly range 34 
THERMOMETER. 
Mean temperature for the month 59.34 
Mean temp, of warmest day, June 30. . 64. 
" " of coldest day, June 15.... 55.66 
Maximum temp, June 30, 2 p. m 80. 
Minimum " " 24, 7 a. m 50. 
Greatest daily variation June 30 27. 
Le-ast " " " 15 7. 
Monthly range of temperature 30. 
Mean daily range of temperature 13.90 
June passed without the excessive warm 
days that usually occur. The mean temper- 
ature was some lower than the average for 
the month, but the mean for the first six 
months was the average of the first half of 
other years. The mean of 1877 w T as 55.18, 
that of 1878; 52.62, making a difference of 
only .44 of a degree. April was warmer than 
the average, and June compensated. The law 
of meteorological compensation seems to be 
well established as regards temperature in 
Oakland, and observations go to show the 
same prevails as regards the rainfall. To es- 
tablish this fact will be of great importance 
to the agricultural interest if to no other. 
ON OUR TABLE. 
Publishers and Authors are kindly re- 
quested to send copies of Books, Keports, 
Pamphlets, etc., or proof-sheets of same to 
the publisher of this paper, for the purpose 
of keeping the scientific world posted on all 
recent publications. 
Illinois State Laboratory of Natur- 
al History. Bulletin No. 2. 1878. Nor- 
mal, 111. 
This volume contains the following papers: 
List of the Aphidini of the U. S. By C. 
Thomas. 
A new species of Aphis (Colopa eragrosti- 
dis). By N. Middleton. 
A list of the Mosses, Liverworts and Lichens 
of Illinois. By J. Wolf and E. Hall. 
A catalogue of the Fishes of Illinois. By D. 
S. Jordan. 
On the Food of Illinois Fishes. By S. A. 
Forbes. 
On the Crustacese Eaten by Fishes. By S. 
A. Forbes. 
Description of a new species of Asellus. By 
O. P. Hay. 
Of these articles the fourth, fifth and sixth 
are especially noteworthy. Much credit is 
due to Professor Forbes for his able manage- 
ment of this institution, which is the only 
purely scientific educational institution ever 
established in the west. 
