400 On the Application of Solar Physics. [J 
since the lowering or raising of the soil would alike open a 
vertical orifice.* 
Then as regards the seasons and their passing features, 
Dr. Hahn has constructed a table of mean temperature, 
from which it would appear that the cold summers and 
winters follow the maximum of sun-spots, and the warm 
summers and winters the minimum ; and, according to his 
view, it is the warmth and dryness of the interval between 
the minimum and maximum period that accounts for the 
appearance at this conjuncture of locusts in Europe. As to 
this last assertion, however, I think some latitude must be 
allowed, as at times stray locusts arrive at the shores of the 
United Kingdom a few years previous to the minimum 
epoch ; nor is it very evident, from Dr. Hahn’s temperature 
table, that the warm years that arrive at the epoch of fewest 
sun-spots last until the succeeding maximum. So then, as 
before, the temperature observations associate the warm 
summers with the minimum of sun-spots, and it is an old 
adage that it is the warm years which bring the locusts. It 
is, however, somewhat satisfactory to learn that the periods 
of multiplication of certain inseCts more disastrous to our 
home-produce than locusts do not coincide here in point 
of time. By referring the species to the orders to which 
they belong, I think we may gain from tabulation that 
crane-flies (Tipulidse) have multiplied in this country at the 
maximum epochs, destructive moths (NoCtuidse at the same 
period ; and that, on the other hand, corn weevils (Rhyncho- 
phora), and perchance certain saw-flies (Tenthredinidse), 
have multiplied at the minimum epochs. 
* When writing my last paper on Solar Physics (“Journal of Science” for 
March, 1882) it had escaped me that Prof. Wolf had already given an approx- 
imation of the sun-spot cycles carried back to 1610, from certain records 
extant : they differ but in few instances from those I have calculated. I also 
should have said (page 158) that the cycles lengthen in all appearance at the 
end of the sixteenth and eighteenth centuries, and are short about 1640 : there 
are certain long periods associated. 
