79G EEPORT— 1898. 



investigation goes on to treat more briefly of other meteor streams, and indicates 

 the dynamical conditions which presumably liave given rise to several remarkable 

 phenomena, such as the various other kinds of shifting radiants, the approximately 

 stationary condition of some of them, the unsymmetrical distribution of some 

 prolonged showers about their maximum, and other effects which have been 

 observed. 



10. Survey of that part of the Scale ujjon which Nature works, about 

 ichich Man has some Information. By Dr. G. Johnstone Stoney, F.R.S. 



11. Tlie Ima()inary of Logic. By Professor G. J. Stokes. 



Absence of a philosophical or logical theory of the imaginary. General adoption 

 of the view that 5 — 1 is uninterpretable in single or pure algebra. Paradoxical 

 character of this position. How can what is essentially meaningless possess an 

 important meaning in its extraneous use? Logical "theory of the imaginary. 

 Derivation from the law of duality. Application to De Moivre's theorem. ' Tlie 

 (Jarnot-D'Alembert paradox. Quaternions. Comparison of the Calculus of 

 Boole's Laws of Thought with that of Grassmanu's ' Ausdehnungslehre.' Pielation 

 of both to ordinary mathematics. 



Department II. — Meteorology. 

 1. Report on the Ben Nevis Observatory. — See Reports, p. 277. 



Report on Meteorological Photography. — See Reports, p. 283. 



3. Report on Seisinological Investigation. — See Reports, p. 179. 



Interim Report on the Montreal Meteorological Observatory. 

 See Reports, p. 79. 



5. A Quantitative Bolometric Sunshine Recorder. 

 By Professor H. L. Callendar, M.A., F.R.S. 



This instrument is essentially a recording bolometer, in which the difference 

 of temperature between a blackened and a bright platinum thermometer of equal 

 resistance is recorded in pen and ink in the form of a continuous curve on a 

 revolving drum. It differs from ordinary sunshine recorders in giving a strictly 

 quantitative record of the quantity of heat received by the earths surface, and not 

 merely the number of hours of bright sunshine. 



The sensitive part of the instrument, wliich is e.xposed to the radiation to be 

 measured, consists of a pair of differential platinum thermometers wound on flat 

 plates of mica, the one black and the other bright, and placed side by side in a 

 horizontal plane so as to record the vertical component of the sunshine, on which 

 the quantity of heat received by the surface of the earth mainly depends. The 

 instrument gives a very complete record of the character of the sunshine, as well 

 as of its intensity. The passage of small clouds, which would leave no trace on 



