TRANSACTIONS OF SECTION A, 559 



Very few experiments have yet teen made ; but the E.M.F of the cells in a 

 battery of Leclaucb^ elements was determined bj- seven experiments, all of which 

 very closely agreed. The value obtained was — 



•00475 

 absolute electrostatic units. 



The author is constructing a battery of 50 Grove cells, specially adapted to the 

 measurement of PIM.F. 



A deflection of the disk is easily observed vnth. about 6 Leclanche cells, or less; 

 — and a second deflection is then taken with a large number — 20, 30, 40, or 50. 



WEDNESDA Y, SEPTEMBER 7. 



The following Reports and Papers were read : — 



1. Be^iort of the Committee on a Stamlard of White Light. 

 See Reports, p. 126. 



2. Bjeport of the Committee on Luminous Meteors. — See Reports, p. 290. 



3. Beport of the Committee on the Thermal Conductivity of Bods. 

 See Reports, p. 126. 



4. A Contribution to the History of the Algebra of Logic. 

 By the Rev. R. Harlet, F.B.8. 

 The author pointed out that the earlier and limited conceptions of algebra, that 

 it is a universal arithmetic, or such a modification of arithmetic as is necessitated 

 by the use of a symbolical language, had prevented for long the connection between 

 the fundamental principles and processes of algebra and of logic from being dis-» 

 covered. To perceive that algebra embraces not only arithmetic in its widest 

 sense, but the whole science of symbolical reasoning, formed a most important step 

 in logic as well as in mathematics. This was first apprehended to some extent by 

 certain of the more philosophical analysts of the earlier part of the present cen- 

 tury, and was more clearly enumerated by Dr. F. Gregory in 1838. Henceforward, 

 as arithmetic had proved the ' science of suggestion 'to algebra, so the latter, in the 

 hands of Boole, proved the science of suggestion to logic. In his works, ' The 

 Mrtthematical Analysis of Logic,' and, more fully and systematically, in his ' Laws 

 of Thought,' he developed the science of logic in algebraical forms. This mode of 

 expression is justified on strictly logical grounds. It is founded, not upon any sup- 

 posed relationship or analogy between the conceptions or ideas with which lof^icians 

 anil mathematicians are respectively conversant, but upon the fact, established by 

 actual examination, that the formal laws of thought in logic are identical with those 

 of an algebra, or science of number, in which the symbols represent, not all numbers^ 

 but only those which we designate by nought and unity. The author next pro- 

 ceeded to consider the symbolical methods in logic which owe their origin to the 

 ' Laws of Thought,' by Boole. He noticed particularly the method of Professor 

 Jevons, as developed in ' The Principles of Science ' ; of Mr. Hugh McOoll in his 

 'Calculus of Equivalent Statements,' and of Dr. Macfarlane, in his 'Algebra of 

 Logic' Eeference was also made to the recently published work of Mr. Venn, on 

 ' Symbolic Logic,' which the author characterised as a powerful defence of th© 

 Booleian method. 



6. On the Illuminating Poivers of Incandescent Vacuum Lamps toith measured 

 Potentials and measured Currents. By Professor Sir William Thomson, 

 M.A., F.B.S., and James T. Bottomley, M.A. 

 The electromotive force used in these experiments was derived from Faure's 



secondary batteries, kindly supplied for the purpose by the Soci<lt^ la Force at la 



Lumiere in their London oflice. 



