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(2) Acting on the suggestion of Mr. Wm. Thomas, Staff Surveyor of Dubbo, T searched some back 
numbers of the Tr •nsactions of the American Society of Civit Engineers, and found that the question of 
the stability of bench marks made on trees was dealt with by Mr. George W. Cooley in a paper read 
before that Society on 3rd October, 1888, and published in 1889, Yol. 20, p. 73. The observations were 
made on the shore of Lake Minnetonka, near Minneapolis, and extended over a period of five or six 
years, being taken yearly about the 1st October. 
Mr. Cooley reports that “No upward growth was discovered, but a change from one to three- 
hundredths of a foot, from year to }’ear, probably caused by action of frost during the winter. The 
gr. a test change in any one year was -03, and the greatest net change in five years -02.” The table given 
b<dow, summarising Mr. Cooley’s tests, will he of interest. 
Total Variation. 
Kind of Tree. 
Diameter 
Inches. 
Year . 
Rise + or Fall — 
Linden 
3 
5 
- 0266 
Iron wood 
12 
i 
+ '016 
Hickory 
3 
0 
- 002 
Linden 
12 
6 
+ -007 
M aple.. 
4 
6 
+ 0134 
Elm. 
4 
4 
- -Oil 
Linden 
5 
5 
- -003 
Elm. 
20 
5 
- -008 
Linden 
18 
o 
- -006 
Linden 
12 
5 
- -012 
Maple... 
20 
5 
- -020 
Ironwood 
10 
5 
- -018 
Black Oak 
12 
5 
- -018 
Maple... . 
10 
5 
- 019 
Maple... 
20 
3 
- -028 
It was further pointed out that “ nails driven into some of the trees, about 4 feet above ground, 
maintained for five years the same relative position with regard to the nails on the benches. Only three 
of these were tested, the others being covered with a growth of bark.” 
It will be seen, therefore, that in the lower parts of these trees no change of any consequence took 
place. But although the observa'ions are most valuable as bearing on the stability of bench marks, they 
do not altogether dispose of the question raised by Mr. Fowler, viz., that the vertical growth of a tree 
extends to the trunk and is not restricted to a prolongation of the branches, for it seems a reasonable 
assumption that if the barrel of a tree grows vertically below the limbs, the greatest extent of prolongation 
would probably take place in the higher part of the trunk. 
Again, that part of the wood which is dressed to form the bench mark usually dies, similar to the 
exposed part of a corner tree from which the bark is removed for the purpose of cutting the numbers, and 
it is well known in the latter case that, should the tree increase considerably in diameter, the originally 
exposed surface will not alter its position horizontally, but become covered with new wood and bark, 
according to the age of the tree, an instance which came under my notice giving a growth of exactly 
(i inches of wood in thirty years on a Eucalypt. 
A set of observations referable to permanent bench marks, and extending to the higher parts of 
several trees, would still afford an interesting and instructive study.—R. H. Cambagf.. 
