PEOCEEDINGS, AUGUST. Xvii 



entitled " The Astronomical Explanation of a Glacial Period." He 

 said that the purport of Sir Robert Ball's paper, which disputed some 

 of the deductioDS of Sir Robert Herschel in his " Outlines of Astro- 

 nomy," shows that the successive periods of glaciation, alternating with 

 periods of genial or tropical temperature, which geologists infer from 

 the indications of the rocks and strata, are necessary corollary from 

 astronomical data. Having fairly stated the conditions of the problem, 

 Mr. Biggs proceeded to say that the statement on which Sir Robert 

 Ball founded his charge against Herschel could only be that on page 

 333 of the fifth edition of Herschel's " Outlines of Astronomy" — '• Sup- 

 posing the eccentricity of the earth's orbit were very much greater 

 than it actually is, the position of its perihelion remaining the same, it 

 is evident that the character of the seasons in the two hemispheres 

 would be strongly contrasted. In the northern we should have a short 

 but very mild winter, with a long but very cool summer, — that i?, an 

 approach to perpetual spring ; while the southern hemisphere would be 

 inconvenienced and might be rendered uninhabitable by the fierce 

 extremes caused by concentrating half the annual supply of heat into a 

 summer of very short duration, and spreading the other half over a 

 long and dreary winter, sharpened into an intolerable intensity of frost 

 when at its climax by the much greater remoteness of the sun." Read- 

 ing this, however, with another extract from the same author, he 

 thought Herschell's meaning would be sufficiently apparent, although he 

 had in this case failed to express himself with his customary preciseness. 

 His statement, said Mr. Biggs, is that " the hemisphere would be 

 inconvenienced . . by concentrating half ^^e" (not its) "annual 

 supply of heat into a summer of short duration," etc., which is, of 

 course, apportioned between the summer of one hemisphere and winter 

 of the other alternately, and he can only be referring to that portion of 

 this " supply " which pertains to the summer or winter of either hemis- 

 phere. That he could have meant nothing else is still more evident from 

 a further quotation (page 230), in which he admits the unequal distri- 

 bution of heat between summer and winter : — " Whenever, then, the 

 8un remains more than 12 hours above the horizon of any place, and 

 less beneath, the general temperature of that place will be above the 

 average ; when the reverse, below ;" that is, the summer and winter 

 portions of the year respectively. The extent of the inequality of the 

 distribution of the annual supply of heat between the summer and winter 

 portions of the year in either hemisphere depends wholly and solely 

 upon the inclination of the earth's axis, and no one could be more cogni- 

 sant of this fact than Sir John Herschel. 



Mr. Stephens exhibited a specimen of an Orthoceratite, belonging to 

 the genus Actinoceras, from the Silurian limestone at Railton, in the 

 Mersey district, and stated thdt he had sent a portion of the fossil, 

 which, when found by Mr. Hainsworth, was in three pieces, to Sydney 

 for identification ; but Mr. Etheridge said that it was not perfect enough 

 to determine the species. The rook in which it was found was the same 

 as that in which extensive borings had been undertaken on the pretence 

 of searching for coal, and that too where the Silurian rock cropped out 

 on the surface, and no coal measures existed. 



TASftlANIAN MOSSES. 



The Secbetary drew attention to a fine collection of Tasmanian 

 mosses, beautifully mounted, and presented to the Museum by Mr. 

 W. A. Weymouth, consisting of 57 specimens representing 50 species, 

 making a total of those previously presented in May last by Mr. 'Wey- 

 mouth, of 117 species. 



The meeting terminated with the usual votes of thanks. 



