i 
AND HORTICULTURE. 7 
It has already been announced that the Finnish Inter- 
national Polar Expedition produced, by experiments made 
on mountain tops, auroral beams and light phenomena of 
the same nature as the auroras, and hence contributed to 
the confirmation of the opinion that auroras are caused by 
electric currents in the atmosphere. The E.M.F. (electro- 
motive force), or the force which produces this current, was 
measured. It was absolutely very little, but always existing, 
though with varying intensity. It is only in exceptional 
cases that it will produce light phenomena—viz., when the 
conditions of the atmosphere are favourable and the current 
is of high intensity. The most important result here is the 
proof of the existence of such a current, which is always 
passing either downwards or upwards. 
The experiments which have been carried out in Finnish 
Lapland, do not, strictly speaking, apply to other regions 
of the earth. Considering, however, that the laws of atmos- 
pheric electricity are nearly the same for all latitudes, the 
existence of such a current in the whole atmosphere seems 
not to be in doubt. 
This electric atmospheric current has hitherto been very 
little investigated ; it is only the atmospheric electricity 
which has been measured. The method has been to, 
measure the potential in a point of the air (or the electrical 
tension of it). These results cannot be used for conclusions 
regarding electrical current from the atmosphere, and, in 
consequence, not for the laws it follows. These observations 
of atmospheric electricity can, however, contribute to some 
general propositions. When it has been found, for instance, 
that the air near the earth’s surface is positive electrically 
(and seldom negative), and that the potential increases 
with the height, a general conclusion can be drawn that an 
electric current, an equalising of the difference of potential, 
is going on between the whole atmosphere and the earth. 
As has been said above, this current: produces luminous 
phenomena or Polar light only when in a state of high 
