152 REPORT—1849. 
extent: the turning-points do not occur in each year in the same months, and ~ 
4 the range of tension differs materially, 
a The year 1847, as we have already 
A. F J. noticed, presents the highest tensions ; 
this is very apparent from the follow- 
ing table of range. 
TaBLeE LVI. 
Mean annual range of the electrical 
tension in the years 1845, 1846 
and 1847, with the mean annual 
range of the three. 
Year. Range. 
1845, 
div. 
1845. 164°4 
1846. 134°0 
1847. 230°0 
—_—_—— 
Mean. 137°3 


1846, 
The greater development of elec- 
tricity in the year 1847 occurred in 
the month of January. The annexed 
curves (fig. 12) are projected on pre- 
cisely the same scale as those of the 
diurnal periods, and are strictly com- 
parable with them, 
On contrasting the annual with the 
diurnal period, we find a marked dif- 
ference which is not of an ordinary 
character. In the diurnal period we 
found an increase of tension towards 
the forenoon, succeeded by a diminu- 
tion, the tension still continuing high 
in comparison with readings obtained 
after 10 p.M.,at which hour the highest 
tension was most usually observed. 
The periods characterized by high and 
low tensions were those at which the 
sun was above and below the horizon 
(speaking in a general sense), the 
development of electricity appearing to 
3 be connected with the increase of tem- 
perature. Inthe annual period the reverse of this takes place : that portion of 
the year during which the sun is further removed from the northern temperate 
zone is characterized by the exhibition of electricity of much higher tension 
than that which is observed during the period when he is nearest thereto. 
From the months in which the greatest and least tensions occur, it appears 
that there is a connexion between the annual curve of temperature and that 
of the electrical tension, the progression of the latter being to a certain ex- 
tent in harmony with that of the former, but inverse. It is well known that 
the same characteristic is presented by the annual curve of humidity, which 
is in inverse harmony with the annual curve of temperature, and this at once 
Mean anaual curves of the electrical tension for the years 1845, 1846 and 1847, with the mean curve of the three years. 

A. 
hel 
ax. 

