RELATIVE AGES OF THE GLOBE'S CATASTROPHES. 169 



a word, the structure of a tooth involves that of the socket in the shonlder- 

 bone, and of the nails, just as to use a mathematical, but very apt illustra- 

 'ion the equation to a curve involves all the properties of the curve ; and 

 as the curve may be drawn when we know the root of the equation, so ir 

 comparative anatomy, by making each property separately the base of in- 

 vestigations, one may deduce all the other properties. Thus the shoulder 

 bone, the articulation of the jaw, the thigh-bone, or any other bone, taken 

 separately, gives the structure of the tooth, or, conversely, from the tooth, 

 a knowledge of these peculiarities may be derived ; so that, taking any one 

 bone, he who is familiar with the laws of the animal economy, may repro- 

 duce the whole animal." Ansted. 



RELATIVE AGES OF THE PRINCIPAL CATASTROPHES OF THE GLOBE. 



From observations, it would seem that the dry land must have appeared 

 in successive portions, to cause on the surface all the variations of nature, 

 form, humidity, and dryness, the combination of which should procure for 

 man all the happiness designed for him by the Creator. The study of the 

 successive appearances of land is now one of the most beautiful points of 

 view in which geology can be presented ; we are indebted to M. Elie de 

 Beaumont for pointing out the course to follow, to establish the chronological 

 order of the principal catastrophes which happened in Europe, and around 

 which all facts of the same nature may be grouped. 



As soon as we perceive some part of inclined sedimentary beds, we may 

 decide that they have been displaced from their ordinary position by up- 

 heaval. The period of this accident remains at first undetermined; but if, 

 at the base of more or less elevated projections which these beds produce, we 

 find other sediments deposited in horizontal strata, 

 resting against the preceding (Ji^. 304), it be- 

 comes evident that the upheaval of the first took 

 place after the formation of the second, which are 

 still found as they were when deposited from r, qru 



water. We now have a term of comparison, and, 



if we succeed in recognising the relative age of the horizontal deposit, we 

 also have an epoch of the catastrophe, relatively determined, which pro- 

 duced the uptilting of the other. These differences of stratification are 

 everywhere seen on the sides of mountains, and we then see that the several 

 sedimentary deposits, a, 6, c, are not all in the same position. In certain 

 places the stratum a, for example, is uptilted, and the stratum b is horizon- 

 tal ; in another, a and b are both uptilted, and c is horizontal ; in a third, a, 

 b, and c, are uptilted together, and another stratum, rf, rests upon them. We 

 must infer, from these observations, that a first upheaval took place after the 

 formation of a, and before that of b ; a second took place between the strata 

 b and c, a third between c and d t &c., and so on, chronologically, as far as 

 they have been observed. 



Systems of upheaval. If the inclined position of sedimentary strata reveals 

 to us the existence of upheavals, the strike or direction of these beds, which 

 is nothing but the line produced by their swelling upwards or the crest or 

 ridge resulting from their rupture, shows us the course followed by the phe. 

 nomerion. Hence it follows we may take one fact for the other, as the basit 

 of observation, and that the different directions (strikes) of mountain chains, 

 are also indications of the different kinds of upheaval. In fact, it has been 

 long and perfectly established, on one hand, that the inclination of strata is 

 intimately connected with the direction of chains, excepting the perturba- 

 tions which result from crossings; on the other hand, we now know that 

 the phenomenon of uptilting of a determinate number of beds extends as far 

 as the chain itself. It has also been ascertained, at least for Europe, that 

 parallel chains correspond,, in general, in the epoch of upheaval ; that is in 



