VOL. XLVIII.] PHILOSOPHICAL TRANSACTIONS, 383 



Mr. Drury found in a stone of the Causeway a rough pebble, in the shape, of 

 an egg, about } of an inch long, and above an inch thick , and when it was 

 polished, it proved to be a white cornelian. They are from 3 to Q sides, fre- 

 quently encompassed with as many stones as there are sides ; but many of them 

 have a narrow side, which has no stone to it, but is filled up with a piece or 

 pieces of stone ; which pieces, when the stones are moved, commonly sepai'ate, 

 and break, off. Some stones have 2 or 3 or more of these sides ; so that it is 

 possible, a stone that has any number of stones round it, may have double the 

 number of sides. 



XXXV. A Letter on the same Subject from the Rev. Richard Pococh, LL. D. 

 Archdeacon of Dublin, to the Rev. Tho. Birch, D.D. Seer. R.S. p. 238. 



Does not contain any important additions to the preceding and other accounts 

 of the Giant's Causeway. 



XXXVI. A View of the Relation between Dr. Halleys Mortuary Tables, and 

 the Notions of M. De Buffbn, for establishing a Rule for the Probable Dura- 

 tion of the Life of Man. By Mr. William Kersseboom, of the Hagu£. 

 Translated from the French, by James Parsons, M. D., F. R. S. p. 230. 



" Man, says M. de BufFon, at the end of the 2d tome, dies at all ages ; and 

 though it may be said in general, that his life is longer than that of almost any 

 other animal, it cannot be denied that it is also more variable and uncertain. 

 Attempts have been of late years made to know the degrees of these variations, 

 and to establish, by observations, some certainty concerning the mortality of 

 mankind of different ages. If these observations were sufficiently exact, and a 

 good number of them made, they would be of great use towards knowing the 

 number of the people, of their increase, of the consumption of provisions, of the 

 division of taxes, &c. Many ingenious men have studied this subject ; and 

 lately M. Deparcieux, of the Academy of Sciences, has given an excellent work, 

 which serves as a rule with respect to annuities for life : but as his principal view 

 was to calculate the mortality of annuitants, and that generally annuitants for life 

 are men in one state, no conclusion can be drawn from it for the mortality of 

 mankind at large. 



" Dr. Halley, Mess. Graunt, Kersseboom, Simpson, &c. have also pub- 

 lished tables of the mortality of mankind ; and they have founded them on ex- 

 tracts from the bills of mortality of some parishes of London, Breslaw, &c. 

 But it appears that their researches, however ample, and the result of loijg study, 

 can afford only very distant approaches to the knowledge of the mortality of 

 mankind in general. In order to inake a good table of that kiryl, not only the 

 registers of the parishes of such cities should be used, where foreigners are daily 



