Scientific Intelligence — T^ology. 183. 



beneath the earth's surface where boiling water heat exists, and 

 water has access, carbonic acid will be driven off from these carbon- 

 ated salts. 



The Soffoni, on Monte Cerboli, &c. in Tuscany, discharging boil- 

 ing-hot vapours from crevices in the limestone, must come from a 

 depth where boiling heat exists, and it is very probable that the 

 accompanying carbonic acid arises from the above-mentioned causes. 

 The same must be admitted for the carbonic acid discharged so abun- 

 dantly in the neighbourhood of the Laacher-See, in the volcanic Eifel, 

 and in other places. These exhalations proceed from the clay-slate 

 formation. According to the laws of the increase of temperature to- 

 wards the centre of our earth, we may calculate that boiling heat exists 

 at a depth of about 8600 feet in these districts, and this depth is cer- 

 tainly within the limits of the clay-slate formation, which is calculated 

 to be at least a mile (German) thick. Calcareous beds (Transition 

 limestone) and quartzose rocks occur at this depth, waters penetrate 

 thereto, and carbonic acid is separated from the limestone as in the 

 above-mentioned experiments. To account therefore for the origin 

 of carbonic acid exhalations, we need no more assume that the focus 

 must be where red heat exists, which presupposes a depth of at least 

 five miles (German) ; for the clay-slate, or any other sedimentary 

 formation, may be the seat of the evolution of the gas, since only in 

 the moderate depth of about half-a-mile (German) the materials 

 required are present. T. R. J. — The (Quarterly Journal of the 

 Geological Society, No. 22, vol. vi., p. 40. 



ZOOLOGY. 



9. On the Increase of the Nail and the Hair in Man. By M. 

 Bertholdt (L*Institut., No. 846, 93.) — The growth of the nails in 

 children is more rapid than in adults, and slowest in the aged. It 

 goes on more promptly in summer than in winter, so that the same 

 nail which is renewed in 132 days in winter, requires only 116 in 

 summer, — a fact depending on the vis vitalis, which seems to be 

 proportional to it. The increase in the nails of the right hand is 

 quicker than for the left ; moreover, it differs for the different fingers, 

 consequently, most rapidly for the middle finger, with nearly equal 

 rapidity for the two either side of this, slower in the little finger, 

 and slowest in the thumb. For the middle finger of the right hand, 

 the nail grew 12 millimeters in 106 days ; for the small finger of 

 the left hand required 88 days more than for those of the right, 

 and also there were produced in this time 3 millimeters less than on 

 the right hand. 



The growth of the hair is well known to be much accelerated by 

 frequent cutting. It forms more rapidly in the day than at night, 

 and in the hot season than in the cold. But it is difl&cult to deter- 

 mine the precise rates. 



It results from the tables accompanying the memoir of M. Ber- 

 tholdt, that the growth of the hair and nails, as well as that of the 



