THE CALIFORNIAN SALMON. 
39 
from the northern to the southern hemisphere, through 
the heat of the tropics. This has now been successfully 
accomplished by the aid of ice and steam ; the one to keep 
down the temperature, and thereby delay the hatching 
process, and the other to shorten the time required for 
transit. 
In the United States of America also, great things have 
been done in fish culture by Livingstone Stone, Seth 
G-reen, Norris, Ainsworth and others, and several large 
establishments exist for fish cultivation. A fish com- 
mission has been appointed by the Government, of which 
the Hon. Spencer F. Baird is president, and with a liberality 
and generosity which does infinite credit to the Great 
E-epublic, they freely supply, not only for their own rivers 
— but also in hundreds of thousands — ova of the salmon, 
trout and coregonus, or whitefish, to stock the waters of 
Australia and New Zealand. The labours of the Commis- 
sion have, in the States, resulted in a manifest increase of 
the fish supply in rivers where the produce had been 
rapidly diminishing, and the benefit which will follow their 
labours can not be easily estimated. In fish culture, the 
hatching of the fish is not the only diifficulty that has 
to be overcome. In many places, high dams or waterfalls, 
prevent the fish from ascending the rivers to spawn. A 
contrivance called aj^sA ladder^ has been invented, by which 
salmon or other sea-going migratory fish, could re-ascend 
the rivers. The fish ladder is simply a series of small 
pools, like steps of stairs, with an opening for the fish to 
get through, and a place where they can rest before 
ascending the next step. The invention has proved ex- 
ceedingly useful, and it has enabled the owners of suitable 
waters, to stock many rivers and lakes with salmon, which 
were formerly inaccessible to migratory fish. 
