434 MR. S..S. "BTTCKMAN ON THE BAJOCIAN [Aug. 1895, 



reader. According to that Table the lapse of three hemerge is un- 

 represented by any deposit yet noted in the Cotteswolds. It is, how- 

 ever, in every way probable that strata were deposited in the basin 

 during these hemerae- — perhaps northwards of any now preserved. 

 An interesting speculation may therefore be indulged in — namely, 

 what thickness would such deposits have attained. One estimate we 

 may obtain from Tables I. and III. (pp. 420, 426), the former giving 

 nearly 14 times the thickness of deposit in the Cotteswolds compared 

 with Dorset in the same length of time, the latter yielding as much 

 as 22 times, and yet being incomplete. Another estimate might be 

 obtained by taking the maximum thicknesses ascertained in Dorset 

 of the same strata as those here tabled, namely about 13 feet, which is 

 rather more than one-third that of the Cotteswolds ; and yet another 

 by taking the total of maximum developments of Cotteswold ' In- 

 ferior Oolite,' which would probably work out to about 400 feet (but 

 exact data have not been collected), and comparing them with the 

 Dorset total of 130 feet. 1 However, in choosing which of these esti- 

 mates to adopt, it must be remembered that the deposits in Dorset for 

 which the probable Cotteswold equivalent thicknesses are desired are 

 not maxima deposits, for the reason that they are very fossiliferous. 

 Therefore the first and last estimates seem the best to take. Now 

 the strata in Dorset deposited during the Satizei-, Humpliriesiani-, 

 and niortensis-hemerse are about 7 feet thick ; it is therefore 

 possible to say that if the Cotteswold sequence had been complete 

 it should have had an extra thickness of at least 7x4=28 feet, 

 or more possibly of 7 X 14 : that is, 98 feet. 



The difference between these figures may seem considerable ; but 

 it is a point gained if the student of Cotteswold geology learn to 

 think that its sequence of ' Inferior Oolite ' is incomplete by some- 

 thing between 28 and 98 feet of rock. There is something, how- 

 ever, of far more importance which warrants the above speculation . 

 In any estimate of the time-value of a hemera, or of a series of 

 hemerae, or in any comparison of one series of hemerae with any 

 other series, the only legitimate measure is the maximum amount 

 of work done by way of deposition in any given time, just as the 

 only comparison of the powers of two racers before they meet is 

 their time over the same distance at utmost speed. No attention 

 can be paid to anything less than maxima ; but it may be conceded 

 that maxima of limestone, of sand, and of clay-deposits would have 

 different values. If, then, the same length of time be represented 

 in the Cotteswolds by a limestone-deposit 14 times as thick as it is 

 in Dorset, any estimate of that length must be based upon the 

 greater thickness. Now the Cotteswold ' Inferior Oolite ' strata are 

 very considerably thicker than those in Dorset ; but, as this paper 

 shows, they are incomplete. Before undertaking any estimate of 

 the time-value of the series of hemerae, it becomes necessary to make 

 some speculation to supply the deficiency ; and that speculation 

 gives a thickness of from 28 to 98 feet as wanting. 



1 ' Bajocian of the Sherborne District,' Quart. Journ. Geol. Soc. vol. xlix. 

 (1893) p. 506. 



