30 



Mr. C. Chree. 



unknown in higher latitudes. This blue patch does not apparently 

 always coincide exactly with the barometric centre. The author's 

 researches show that in middle latitudes the formation of a bull's-eye 

 does not take place when the motion of translation is rapid ; but as 

 this blue space is not observed in British cyclones when they are 

 moving slowly, it would appear that a certain intensity of rotation is 

 necessary to develop this phenomenon. 



The trough phenomena — such as a squall, a sudden shift of wind 

 and change of cloud character and temperature just as the barometer 

 turns to rise, even far from the centre — which are such a prominent 

 feature in British cyclones, havq not been even noticed by many 

 meteorologists in the tropics. The author, however, shows that there 

 are slight indications of these phenomena everywhere ; and he has 

 collated their existence and intensity with the velocity of propagation 

 of the whole mass of the cyclone. 



Every cyclone has a double symmetry. One set of phenomena such 

 as the oval shape, the general rotation of the wind, the cloud ring, rain 

 area, and central blue space, are more or less related to a central point. 

 Another set, such as temperature, humidity, the general character 

 of the clouds, certain shifts of wind, and a particular line of squalls, 

 are more or less related to the front and rear of the line of the trough 

 of a cyclone. 



The author's researches show that the first set are strongly marked 

 in the tropics, where the circulating energy of the air is great and the 

 velocity of propagation small ; while the second set are most prominent 

 in extra- tropical cyclones, where the rotational energy is moderate 

 and the translational velocity great. 



The first set of characteristics may conveniently be classed together 

 as the rotational ; the second set as the translational phenomena of a 

 cyclone. 



Tropical and extra-tropical cyclones are identical in general 

 character, but differ in certain details due to latitude, surrounding 

 pressure, and to the relative intensity of rotation or translation. 



" Conduction of Heat in Liquids." By C. Chree, B.A., 

 King's College, Cambridge. Communicated by Professor 

 J. J. Thomson, F.R.S. Received March 31, — Read April 

 21, 1887. 



The conduction of heat in liquids has of late years been considered 

 by several observers in Germany. In this country Mr. J. T. Bottom- 

 ley and Professor Guthrie carried out experiments a good many years 

 ago, but in neither case do the results agree well with those obtained 

 abroad. In all the more recent methods the conduction has taken 



