244° Dr. Wallace on 
The great question of the return of sewage to the soil, the in- 
troduction and acclimatization of new species of plants, insects 
and animals, are problems presented to this age for solution. It 
is the duty of man, by patient investigation, to arrive at a correct 
interpretation of nature’s laws, and apply them successfully to his 
own benefit. ‘The process is a slow one, and many mistakes 
iust be made before the truth can be elicited, but success in the 
end is certain, 
In conclusion, it is worth while to note the remarkable events 
which have heralded the dawn of Ailanthiculture: 115 years ago 
the Ailanthus glandulosa was brought to Europe, and _ thence- 
forward acclimatized, but not for the purpose of Sericiculture : had 
the silkworms been then imported, they could not have been 
reared for many successive years for lack of foliage; time was 
required for the tree to become naturalized, and to spread over 
Europe, Canada, Australia, &c., to manifest its hardy and repro- 
ductive nature, and to become known to cultivators. Then came 
a severe epidemic disease affecting the varieties of the Bombyx 
Mori feeding on the mulberry tree, causing severe loss to the 
cultivators, and distress among the poor in the silk-producing 
districts. Hence arose a cry to revert to the original silk-produc- 
ing countries, China and Japan, for new and healthier races, and 
also for new and hardier species. ‘These views received practical 
encouragement from the Minister of Agriculture in France, and 
from the Emperor. But without the aid of missionaries, those 
pioneers of religion and civilization, neither the Ailanthus tree 
nor the silkworm that feeds on it would ever have reached 
Eu-ope, and the efforts of the French Emperor and of the silk 
manufacturers would have been in vain. The missignary must 
first pierce and penetrate China before the merchant can extract 
her jewels. Various political movements, coincident in point of 
time, opened up more thoroughly the Oriental silk districts to Euro- 
pean research. The employment of steam power shortened consi- 
derably the transit, and affording facilities of rapid movement, both 
threw open to investigation regions hitherto unexplored, and per- 
mitted the conveyance to Europe of living cocoons and eggs. 
The Ailanthus silkworm is in 1856 discovered and sent to 
Europe; its food plant, the Ailanthus tree, is already acclimatized, 
and awaiting in abundance its advent, so that the insect is easily 
multiplied and naturalized. Then comes a crisis in the cotton 
trade: owing to the American war the supply fails, and substi- 
tutes for cotton are eagerly sought after. Hence, Ailanthiculture 
