18 ON THE DECADENCE OF AUSTRALIAN FORESTS ; 
actors in the work of destruction cannot be doubted, but 
were it not for their evident sincerity such an explanation 
would scarcely attract attention. 
Another explanation which has sometimes been suggested 
is that a kind of grub attacks them, and having found its 
way into the sap between the wood and the bark, it con- 
tinues its work of exploration so effectually that the flow of 
the sap is interfered with and the trees sicken and 
die. The tunnelling of numerous grubs may be seen 
under the loose bark of dead saplings when it peels off the 
stem; the appearance is familiar to those who have had 
to strip the bark from sapling rails when it begins to 
loosen; but the grub in this case does not commence his 
work until after the saplings have been cut and begin to 
dry. 
Others have suggested that the trees have died because 
there has been too much rain; because there has been too 
little rain; or because of excessive cold in the more severe 
winters. These are some of the principal reasons which 
have been urged in the way of explanation, and it is not 
improbable that there is some truth inthem. At least they 
are entitled to as much consideration as the theory of the 
opossums or that of the grubs. 
The difficulty which immediately crops up when an 
attempt is made to solve the question, is the impossibility 
of obtaining any reliable data upon which to work. My 
personal observations have led me to believe that the 
causes of the decay of forests are partly climatic and partly 
artificial, or, in other words, the effect of the treatment 
which the country receives from the operations of the 
people who occupy it. But without being able to fix the 
time when the trees became affected, and to ascertain the 
character of the seasons antecedent to those marked 
changes, it is impossible to offer anything more reliable 
than a theory which may possibly help others to trace the 
cause at some future time. I shall claim therefore to make 
nothing more than a suggestion in this paper, that others 
may test its value, or otherwise, by their own experiences. 
The district of New England is subject to sudden and 
severe changes of temperature, and although, on account of 
its elevation, the rainfall is more frequent than in the lower 
