TRANSACTIONS OF SECTION A. 577 



traces of iron, which are found in even the best purchased sulphate of zinc. The 

 sulphate of zinc solution may also contain basic sulphates, and it is not homo- 

 geneous after any variations of temperature. This gives rise to variations of the 

 electromotive force of the cell, and also to large variations of temperature-coeffi- 

 cient. The mercurous sulphate bought as pure nearly always contains a great 

 deal of mercuric sulphate. The effects of these and other causes of variation are 

 discussed, and an amalgam cell, preferably with a non-saturated solution, recom- 

 mended. 



3. A Joint Discussion with, Section G. on Units and their Nomenclature was 

 opened hij Professor Oliver J. Lodgk, F.B.S., folloived bu W. H. Pkeece. 

 F.B.S. 



The following Papers were read in connection with the discussion, viz. :— 



Some Revolutionanj Suggestions on the Nomenclature of Electrical and Mechanical 

 Units. By Professor W. Stroud. 



Present Practiml System of Units.—l. The present practical system of units 

 is very objectionable on three grounds — 



(a) There is no prima facie reason why the practical unit of current should 

 be equal to 1-lOth c.g.s. unit. 



(/3) The relation between the other practical electric units and the correspond- 

 ing c.g.s. units is much more complex than need be. 



(y) The units of work and power are far too small for practical requirements. 



2. If we were starting to devise a practical system to-day, such a system could 

 best be formed by taking lO^cm. as the unit of length, 10-"gm. as the unit of mass, 

 and the second as unit of time. 



3. That in the interests of the ' practical ' men of the future and in the inter- 

 ests of _the_ electrical students of both the present and the future, it is highly desir- 

 able to initiate a revolution with the object of dethroning the present practical system 

 of units. 



Nomenclature.— 1. That the term Dyne to indicate 10^ of our present (1891) 

 dynes is objectionable, as custom has restricted the use of Greek derivatives entirely 

 to c.g.s. luiits. 



That 10' dynes, if required, might be called a Hebdomodyne, suitably con- 

 tracted, of course, or preferably a joe (joule over centimetre). 



2. That the classical languages are of little or no service for the provision of 

 names for modern, more or less complex, physical conceptions, and therefore this 

 method of coining words it is desirable to abandon. 



3. That for c.g.s. units some system of automatic 7io7nenclature m which every 

 name shall be self-explanatory would prove a boon to the teachers and a blessing to 

 the student, and that such a system is quite capable of being devised. 



4. That the prefixes meizo to indicate lO^, and mei to indicate 10-' may be 

 found useful. 



On a Table to Facilitate the Conversion of Electrostatic and Electromagnetic 

 Measures into one another. By G. Johi;soh^e Stoney, M.A., D.Sc, F.B.S. 



The fundamental equations of electricity are :^ 



^ = '*'^> for the repulsion between two quantities of electricity. 



oPP' 



^ = *'— 2-> for the repulsion between two quantities of magnetism, and 

 1891. ' 



