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Electrical Measurement op Temperature of Steel and Invar Measuring-bands. In conjunction with Professor T. H. Laby, experiments are being carried out*atyVictoria"College on the electrical measurement of temperature of steel and invar measuring-bands. Two concrete blocks have been put in 4 chains apart; one block is 2 ft. square on the bottom, 10 in. square on top, and 2 ft. 6 in. high, while the other is 3 ft. square on the bottom, 10 in. square on top, and 6 ft. high ; the difference in size being necessary owing to the slope of the ground. These blocks carry the marks with which the bands are compared. High-power microscopes are mounted over the marks. The bands are supported at every chain on large wheels 3 in. in diameter mounted on ball-bearings and insulated. The bands are anchored to a straining-post at one end, and are strained by weights at the other end. An electric current from a small accumulator is sent through the steel band, and returns by a piece of insulated flexible copper wire, and passes through a sensitive galvanometer and a resistancebox. The variation of the temperature of the steel band alters its resistance, and by measuring the resistance the true temperature of the band is obtained. Preliminary experiments seem to show that the results will be of high accuracy, and that a portable and convenient field outfit can he designed for use on base measurements and on standard surveys. Standard Bar and Comparator. This apparatus was obtained from the Cambridge Scientific Instrument Company, England, and will be the final standard of length for the measurements of the bases of the triangulation. The copies of the certificates of examination give a good description of the apparatus and show its high accuracy. National Physical Laboratory, Teddington, England. — Copy of Certificate of Examination of a 10-link Scale. For Lands and Survey Department, Wellington, New Zealand. Description : H form section. Total length, 207 cms. ; width, 3 cms. ; depth, 3 cms. Four pairs of brass supports fit into the groove of the bar and act as holders for thermometers. Marked : On front —Standard Bar No. 1, Lands and Survey Department, Wellington, New Zealand, Made by the Societe Genevoise, Geneva, for the Cambridge Scientific Instrument Company, Limited. On back—Acier Nirkel 43% Coulee 2432. 162. No. 9407. Graduations : The graduations are on the neutral plane of the bar, and are marked and numbered at each T \j link throughout. The ends are engraved A and B, left and right respectively. At end A a space from ■£$ of a link to the left of the zero mark to the 0-1-link mark is divided to 0-001 of a link. At end B a space from 9-9-link mark to ¥ \j of a link to the right of the 10-link mark is divided to 0-001 of a link. The spaces of a hnk on'either side of each link-graduation are also divided to 0-001 of a link. The scale, symmetrically supported on two rollers 118 cms. apart, has been compared with the Laboratory standards, and the lengths at 0° Centigrade between the various link-graduations have been found to be as given below : — Actual Lengths at 0° C. Graduations. Links. 0-1 .. LOOOOI 3 0-2 .. 2-00004! 0-3 .. 3-00003 4 0-4 .. 3-99999, 0-5 .. 5-00002 3 0-6 .. 6-00002, 0-7 .. 7-00001 „ 0-8 .. 7-99996, 0-9 .. 8-99991 9 0-10 .. 9-99992 4 The above results may be relied on as accurate, for the shorter lengths to within about 3 units. and for the longer lengths to within about 5 units in the last (dropped) decimal place. The coefficient of linear dilatation of this scale has been determined between the temperatures 0° C. and 31° C, and the length of the scale at other temperatures than 0° C. has been found to be given by the following formula : — Lt = Lo (1 + 0-00000714 t + 0-000,000,000,39 t 2 ) the temperature being expressed in the hydrogen scale. (Signed) B. T. Glazebrook. Director. September 25th, 1912. Eef. M 105, 46. National Physical Observatory, Teddington, England. — Copy of Certificate of Examination of a 10-link Comparator. For the Lands and Survey Department, Wellington, New Zealand. Description : This instrument consists of a firm base carried on three levelling-screws. A nickelsteel shaft, somewhat longer than 10 links, is supported on four hardened-steel rollers, which are connected to the base, and which allow free longitudinal movement of the shaft. Two microscopes, placed any distance apart from 6 cms. to 208 cms., can be gripped in the shaft. The position, of the microscope shaft is controlled by a micrometer-screw, suitably mounted on the base, two springs keeping the shaft and the end of the micrometer-screw in contact with the two ends of a connecting-rod. Makers : The Cambridge Scientific Instrument Co., Ltd. Marked : The Cambridge Scientific Instrument Co., Ltd., Cambridge, England, No. 14338 M 3 9406. This instrument has been examined at the Laboratory, and its workmanship has been found to be satisfactory.