776 KEPORT— 1903. 



Protective Devices may be divided into two classes : 



(1) Circuit breakers. 



(2) Devices which prevent or relieve excessive rises of pressure. 



Class 1 may be again divided into two subdivisions : (a) Fuses ; (b) Switches. 



The action of two types of fuses is discussed and curves given showing the 

 difference between the two types. 



The oil-break switch is found to be the only workable type for large powers, 

 and the details of operation of such switches are gone into. 



The automatic attachments for opening the switch on overloads and reversals of 

 power are described. 



Class 2 includes charging devices, which the author considers unnecessary, and 

 spark-gaps of which a new type of oil immersed spark- gap is described, which, the 

 author considers, will safeguard a system from undue pressure-rise. 



3. Aluminium as an Electrical Conductor. By J. B. C. Kershaw, F.I.G. 



The increasing use of aluminium as an electrical conductor for bare overhead 

 transmission lines, especially in the United States, and the claims made for this 

 metal as a substitute for copper, led the author in October 1899 to commence a 

 series of exposure tests at two localities in Lancashire, England. 



These tests were made in order to ascertain the resistance to corrosion ofl'ered 

 by commercial aluminium rod and wire under the conditions obtaining, with 

 exposed bare overhead wires. Samples of aluminium rod and wire were obtained 

 from the principal English firms, and in order to make the series of observations 

 more complete, samples of galvanised iron wire and of copper and tinned copper 

 wire were also submitted to atmospheric exposure. The methods of observation 

 and the results obtained during the first exposure period (from October 1899 to 

 August 1900) were described by the author in a paper read before the London 

 Institution of Electrical Engineers on January 10, 1901. This paper was reported 

 in most of the English and foreign technical journals. 



The present paper is the record of the observations made since the date named 

 above, and it contains the chemical and physical tests of the aluminium wires 

 exposed at Waterloo, Lancashire, together with the results obtained during two 

 further periods of exposure, namely, from August 22, 1900, to November 6, 1901 , 

 and from November 9, 1901, to December 4, 1902. 



Since it may be considered unnecessary to repeat much of the information con- 

 tained in the Electrical Engineers' paper of January 1901 the author proposes to 

 treat the present paper as a continuation of that of 1901, and to simply bring the 

 tables and information of the earlier paper up to date. 



The author then deals seriatim with the following points: (1) Production and 

 price ; (2) Relative costs of copper and aluminium ; (3) Installations of 

 aluminium for conducting purposes ; (4) Durability tests of aluminium and 

 other metals under atmospheric exposures ; and concludes his paper with the 

 following summary of the results obtained in the exposure tests at Waterloo : 



' Summarising the results recorded in Table II., we may say that all the 

 samples of aluminium gained in weight during exposiu-e, and that all were pitted 

 and corroded, especially on the under side where the water drops had collected 

 and dried. The rods appeared to have suflered rather less than the wires, and it 

 is therefore probable that in the course of drawing down, aluminium wire under- 

 goes physical change. 



'The author does not wish to base any unfair conclusions upon the results 

 obtained in these exposure tests. He may, however, claim to have proved that 

 some of the aluminium rod and wire which was being manufactured and sold in 

 England for electrical purposes in the years 1899 and 1901, was not able to 

 stand atmospheric exposure on the coast of Lancashire without corrosion. It is 

 only a fair deduction from these exposure tests to assert that aluminium manu- 



