Brarm.—On the Building Materials of Otago. 171 
midsummer is the best ;" but Mr. Kirk gives a decided opinion in favour of 
winter felling. He fixes April to August as the most suitable time in all 
the forests south of Banks Peninsula. I have no doubt Mr. Kirk is correct 
in considering this the season in which the trees are freest of sap, for the 
distinctness of the annual rings in most Otago timbers shows a decided 
period of repose in the growth. Still it is quite possible that a similar con- 
dition exists during the two summer months, December and January, and 
I would have little hesitation in including them in the felling season. I 
have instituted a series of experiments with the view of assisting in deter- 
mining the season when the trees contain the minimum quantity of sap ; it 
consists in observing the strain required to tear off strips of bark in each 
month of the year. The experiments will not be complete for six months, 
so I eannot give the results in this paper, but will do so on a future occa- 
sion if it is found to be worth publishing. The only well authenticated 
proof I have obtained of the superiority of winter felling in New Zealand is 
given in Mr. Horman's fence at Makerewa, already referred to. All the 
black pine posts erected in the winter of 1861 are still in good preservation, 
while those felled and erected a few months subsequently were more or less 
decayed some years ago. Assuming that ripe trees only are felled, and that 
none of the sap-wood is used, the time for felling timber is, within certain 
limits, of secondary importance to its subsequent seasoning and desiccation. 
The simplest way of obtaining a fair amount of seasoning in New Zealand 
would be to bark the trees in spring, cut them in the following winter, then 
slab the logs and let them lie in a running stream for a few weeks, or, what 
is better, let the sawn scantlings be submerged. There is little trouble in 
doing this when the timber is cut up in the bush as at Catlin River and 
Southland. After having the sap washed out in this way, the timber should 
be thoroughly dried under cover in open shed. 
Table III., which gives the results of some experiments I made, shows 
the absolute necessity of seasoning ; —it gives the weight of water in a cubie 
foot of green timber, and the transverse shrinkage in boards twelve inches 
square and half an inch thick. The results may be accepted as a fair indi- 
cation of what will be obtained in practice, for the samples were picked 
heart-wood, eut radially to prevent warping ; but they were taken from 
green logs and subjected to severe drying at a fire, and in the hot air of the 
— Turkish baths. It will be seen that the greatest contraction is in ribbon- 
wood, next the red birches, and after that the hardwoods generally; the 
least is in black and white pine. It is worth noticing that English oak and 
New Zealand red birch, members of the same botanical family, are both 
given to excessive shrinkage. I should add that the results in Table III. 
are not higher than would be obtained from European and American timbers 
of the same class. 
