[345]

22

[annotated table]

Tertiary Cretaceous Oolite New Red Permian &

endured what say 45 [illeg]

These lines represent duration of species which have not existed the whole of Tertiary period from Brown.

and then calculate how broad these vertical bands wd be if all came in same rate, though of course this too much to assume.

I suppose it wd be right to measure the sum total of length of lines, representing those species which do not live all the time, & they by rule of those calculate how long the main body ought to be..No no. It is the [illeg] in which chiefly concerns these views

[in margin:] Very few will be found to come in & die out within the period in Creation

345v]

The problem is to discover duration of species from seeing how many come in after the commencement of & die out before the end, within the given period - or both come & die within the limit of the period.

If I know that in certain island, that during 10 years there lived altogether 1000 men; & knowing population of country

Taking a single year; if you knew how many men die & are born, & both die & born in this year, can the duration of life be calculated.

Including all those born & died within the 10 years; & that I further know that 5 were born & 5 died & 2 both were born & died, can the average of life of these inhabitants be calculated??

I think this is right.