THE WEATHER IN THE BRITISH ISLES. 85 
any rule can be framed by which the greater or less quantity of 
ice that will be detached from the Arctic Regions, and the times 
when it will be detached in any year, can be calculated, though 
it may be reasonably supposed that the earlier and warmer the 
summer in the Arctic Seas, the more ice will be detached, and 
consequently the wetter will be the summer in England. 
England and Western Europe not only enjoy in the Gulf 
Stream a power that tempers the coldness of the sea around them ; 
an analogous effect on the air above those countries is produced 
by the ever glowing surface of the Great African Desert south- 
ward. The air which is heated over those burning sands and 
rocks expands and diffuses its glow over Europe. Its most 
violent effects are exerted eastward in the Simoon and Samaél or 
“wind of death’? of the Arabs, and towards the north-east in the 
Sirocco of the Levantines; only its milder effects are felt in 
Western Europe. 8. 
August 23, 1866. 
American Buicur.—This common insect (Aphis lanigera) which 
infests apple trees, produces in the course of a season eleven 
broods of young. ‘The first ten broods are viviparous, or are 
brought forth alive, and consist entirely of females. These never 
attain their full developement as perfect insects; but being only 
_ in the larve state, bring forth young, and the virgin aphides thus 
produced are endowed with similar fecundity. But at the tenth 
brood this power ceases. The eleventh does not consist of active 
female larve alone, but of males and females. These acquire 
wings, rise into the air, and sometimes migrate in countless 
myriads, and produce eggs, which, glued to twigs and leaf-stalks, 
retain their vitality through the winter. When the advance of 
spring again clothes the plants with verdure, the eggs are hatched, 
and the larva, without having to wait for the acquisition of its 
mature and winged form, as in other insects, forthwith begins to 
produce a brood as hungry, and insatiable, and as fertile as itself. 
Supposing that one aphis produced 100 at each brood, she would, 
at the tenth brood be the progenitor of one quintillion of de- 
scendants (1,000,000,000,000,000,000).—H. Parsrson. 
F 
