TBANSACTIONS OF SECTION A. 591 



the whole length of strip is about 5J feet, and from the two ends the galvano- 

 meter and battery leads respectively project. 



A very flexible quadrilateral is thus obtained in the form of a ribbon, which can 

 be wrapped round any apparatus whose temperature is required. 



Since the two wires, which together form the quadrilateral, have different tem- 



Eerature coefficients, there is no balance except for one particular temperature ; 

 ut the balance can be restored by shunting either the wire AB or the arm BC 

 by connecting a resistance-box in a suitable manner with the projecting leads. The 

 resistance of the shunt reqiured to produce a balance can be employed to indicate 

 the temperature when the instrument has once been graduated. The graduation 

 of the apparatus exhibited was made for the author at the Cavendish Laboratory 



GALVANOWeTER. 



by Mr. J. W. Capstick, demonstrator at University College, Dundee. The ribbon 

 was woimd round a metal cylinder, and the whole immersed in ice or water, and 

 a number of readings of the shimt taken at different temperatures between 0° and 

 28° C. The conductivity of the shunt at different temperatures is very nearly 

 represented by a straight line cutting the zero line at the neutral point IS-IG'' C, 

 The maximum divergence from the straight line corresponds to the temperature 

 difference of a fifth of a degree between 0° and 15-16° and to about a tenth of a degree 

 between 15-16° and 28°. In the graduation the temperatures are referred to the 

 Kew standard by means of mercury thermometers previously compared at Kew. 

 The temperature can be read with a suitable galvanometer to about the 500th of a 

 degree. 



12. Fourth Report of the Committee on Standards of Light. 

 See Reports, p. 29. 



TUESDA Y, SEPTEMBER 11. 



The following Papers and Report were read : — 



1. Joint Discussion loith Section G on Lightning-conductors. 



The President called upon Mr. "W. H. Preece, F.E.S., and Professor Oliver J, 

 Lodge, F.R.S., to open a joint discussion with Section G on Lightning-conductors. 



Mr. Peeece said it was a most remarkable thing that if they wanted to know 

 much about atmospheric electricity and its effects they had to go back to the works 

 of Benjamin Franklin 140 years ago. Scarcely anything had been done in this 

 direction since then. Up to the year 1881 there was not even a code of rules 

 extant in this United Kingdom to guide people in protecting their buildings from 

 the destructive effects of atmospheric electricity. It was proposed in 1878 to 

 establish a conference of various societies to discuss the effects of atmospheric 

 electricity and to form a code of rules for the erection of lightning-conductors. 



At the York meeting of the Association in 1881 a report was adopted; it was 

 then published, and was one of the most admirable works that had ever been 

 collated on atmospheric electricity and its effects. 



Now that report was divided into three parts. In the first part was discussed 

 the purpose which a lightning-conductor was intended to serve. In the second 

 part there was a statement of those features in the construction and erection of the 

 lightning-conductors respecting which there had been, or was, a difference of 

 opinion, and the final decision of the Conference thereupon. In the third part 



