484 Probable Extension of Solar Physics . [August, 
extremes of solar power, they often originate, and in cases 
can be traced to, a multiplication of species that has trans- 
pired during the minimum period. Especially is this 
probable with regard to the locust inroads which, pushing 
northwards, have found their chroniclers since the Christian 
era, and which, from unknown climatic or agrarian reasons, 
appear formerly to have been more formidable or more, 
dreaded by an ignorant population. Another minor migra- 
tion of European inserts, much less marked, occurs in the 
same direction as the greater flights between the maxima 
and minima sun-spots, or when the index points at 38*5 ; I 
am, however, unable at the present moment to affirm 
whether this faunistic displacement should be attributed to 
the greater or less period of solar force. 
I think I have here adduced sufficient to show the im- 
portance of solar physics, and to indicate their probable 
line of extension to a common ground where the man of 
merchandise may meet with his scientific brother, and learn 
the reason of his triumphs and losses, which, by being 
recorded, may eventually be remedied. But not alone the 
merchant ; the astronomer likewise has somewhat to learn 
of the entomological record, for he will here find ready data 
which when elaborated will allow him to extend his solar 
cycles back into the Dark Ages which preceded Schwabe 
and Galileo, and in this wise : — Since on tabulation it will 
be seen, even at first sight, that ancient locust invasions in 
Europe have taken place at intervals that homogenise with 
those following modern migrations ; and since the latter in- 
tervals come on at the maximum of spots, when the inse< 5 ts 
regularly disappear and the ravage ceases ; few will doubt 
but what in collating the evidence of the havoc we are vir- 
tually pointing the sun-spot maxima. So from what has 
been before adduced the minimum periods may be similarly 
approximated and fixed, by correlation of the records of 
locust multiplication in localities situated on the edge of the 
northern tropic, as, for example, the districts of southern 
Europe and northern Africa, Persia, or China. 
