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(With I figure in the text)A new type of dendrometer was privately described by Pyke in 1941, but no account has yet been published. The writer was able to reconstruct a number of Pyke's original instruments from portions found in laboratories of the Rubber Research Institute of Malaya after the war, and the following notes give details of one such dendrometer.The essential features are shown in Fig. i. A steel U-shaped frame {A) 23 cm. across, fits around the trunk of the tree. At diametrically opposite points on the trunk hollowground brass studs are fastened with grafting wax or plasticine to cleaned areas of bark, and bearing points {B) and (C) on the instrument make contact with these studs. The bearing point {B) is the end of a lock-nutted thumbscrew, which can be adjusted over a range of about 2 cm. (In the diagram the lock-nut is hidden by the frame.) The bearing point (C) is a hemispherical stud at the end of a lever. The lever is mounted on a flexible steel strip (watch spring) at {D), which gives it a definite pivotal motion, but allows no movement whatever in other directions. 'Bellying' of the strip is prevented by two studs beneath the pivot. The lengths of the lever on each side of the pivot are 4 and 8 cm. respectively, giving a ratio of movement between the ends of 1:2. When the dendrometer is mounted on a tree the bearing point (C) is held firmly in position by the action of a light tensioning spring {E).A rod (F) is attached to the longer end of the lever by a short length of watch spring. This rod which is 22-5 cm. long consists of a zinc portion (7-5 cm. long) and a brass portion (150 cm.). These proportions ensure that the linear expansion or contraction of the rod per degree change in temperature is exactly twice the linear change in dimensions of the frame in the same direction. With a i: 2 leverage at the end of the lever operating the rod {F) thermal effects are thus cancelled out, and are not transmitted to the remainder of the system. The rod (F) emerges through a hole in the frame and is attached by a short length of watch spring (G) to a brass block (//), itself attached by two strips of watch spring (/), to the frame. A polished steel stud {J) is let into the top of the block {H); the block is I cm. deep and 2 cm. from the rear edge to the centre line of this stud, giving a vertical movement to the stud twice as great as the horizontal movement of the rod {F) and a total magnification at the bearing point {J) of four times the original movement of (C).Attached to the frame are two polished steel bearing plates {K), {K). On these ride a rocking bar (L) with three bearing studs, two {M, M) resting on the plates, the third (A^), which is displaced 2 mm. from the axis of the other two studs, riding on the steel bearing plate {J) on the block (//). Movement of the block {H) thus imparts a rocking motion to the bar (L). To one end of this bar is attached an adjustable balance weight; to the other a pointer 20 cm. long. The ratio of movement between the block {H) and