164: THE OENESTS OF SCIENCE. 



by the introduction of some kind of currency, we find 

 that the oneasures of worth, constituting this currency, 

 are organic bodies ; in some cases cowries, in others 

 cocoa'7iuts, in others cattle, in others pigs ; among the 

 American Indians peltry or skins, and in Iceland dried 

 fish. 



Xotions of exact equality and of measure having been 

 reached, there came to be definite ideas of relative magni- 

 tudes as being multiples one of another ; whence the prac- 

 tice of measurement by direct apposition of a measure. 

 The determination of linear extensions by this process can 

 scarcely be called science, though it is a step towards it ; 

 but the determination of lengths of time by an analogous 

 process may be considered as one of the earliest samples of 

 quantitative prevision. For when it is first ascertained 

 that the moon completes the cycle of her changes in about 

 thirty days — a fact known to most uncivilized tribes that 

 can count beyond the number of their fingers — it is mani- 

 fest that it becomes possible to say in what number of days 

 any specified phase of the moon will recur ; and it is also 

 manifest that this prevision is efiected by an opposition of 

 two times, after the same manner that hnear space is meas- 

 ured by the opposition of two fines. For to express the 

 moon's period in days, is to say how many of these units 

 of measure are contained in the period to be measured — is 

 to ascertain the distance between two points in time by 

 means of a scale of days, just as we ascertain the distance 

 between two points in space by a scale of feet or inches : 

 and in each case the scale coincides with the thing meas- 

 ured — mentally in the one ; visibly in the other. So that 

 in this simplest, and perhaps earliest case of quantitative 

 prevision, the phenomena are not only thrust daily upon 

 men's notice, but Nature is, as it were, perpetually repeat- 

 ing that process of measurement by observing which 

 the prevision is efi\3Cted. And thus there may be signi- 



