344 Professor J. Joly — Salt and Oeological Time. 



gravel beds containing the bones of extinct animals, but lying about 

 on the surface, their age being therefore quite indefinite. To call 

 them paleeoliths seems a misnomer, for that term has an archaeological 

 sense in Europe and defines a geological horizon which it is im- 

 possible to equate with anything in Africa, where traces of the 

 catastrophe we have mentioned and of the gap which it caused 

 are not available. And if we are to justify the use of the terra, 

 it must be apart altogether from its defining a geological period 

 or a particular archeeological horizon, and merely as marking 

 a stage of culture. Hence we have had recently a mighty fight, 

 which has been largely upon the connotation of a name. This 

 fight has occupied the pens of Sir John Evans and Dr. Forbes, 

 both of whom have written with the skill and knowledge that 

 might have been expected of them. The issue has been com- 

 plicated by the fact that Africa north of the Atlas Mountains 

 is zoologically and arch£eologically a part of Europe. In Algiers 

 evidence is ample that the same destruction of Pleistocene animals, 

 marked by their rapid entombment in gravel and brickearth, took 

 place as occurred in Europe ; and there, as in Europe, the traces of 

 Palseolithic man, properly so called, have been found in the gravels 

 and drift-beds associated with the extinct beasts, a fact to which 

 Sir John Evans has called especial attention. In the valley of the 

 Nile similar remains of man were found long ago by General Pitt- 

 Eivers in the breccias and coarse gravels of the great valley, and 

 here also may claim to be truly Palaeolithic. But in the case of the 

 surface implements from Somaliland and the country of the bushmen, 

 we must, if we are to be precise, be careful that in applying the 

 term Palaeolithic we do not in some way imply great age, for all it 

 may mean is a mere survival, just like the survival of the stone 

 lamps of the Esquimaux and the stone pots and pans of the 

 Hebridean cottiers. 



II. — The Cikoulation of Salt and Geological Time. 

 By Professor J". Joly, M.A., D.Sc, F.E.S. 



FEOM time to time I have received from correspondents 

 suggestions that the method of determining the geological 

 age of the Earth by the rate of solvent denudation of sodium might 

 be open to considerable error if the allowance made in my paper 

 (Trans. R.D.S., ser. ii, vol. vii), for sodium chloride carried from 

 the sea by winds and washed from the atmosphere by rain, was 

 seriously at fault. These suggestions arise from incomplete study 

 of the quantities involved. Had more space been given in my 

 paper to this question, the hasty criticisms I have had to contend 

 with, doubtless, would be less often advanced. The whole matter 

 is capable of the simplest arithmetical statement, and the limit of 

 error arising from this source easily defined. Recently one 

 gentleman has written at considerable length on the matter in the 

 pages of the Chemical News. I have replied to Mr. Ackroyd in 

 that journal. But the definition of the limit of error referred to, 



