1012 



SCIENCE. 



[N. S. Vol. XI. No. 287. 



made, the record should reflect the persist- 

 ence and the regularity of the inciting 

 rhythm. 



The search of the rocks for records of the 

 ticks of the precessional clock is an out-of- 

 door work. Pursued as a closet study it 

 could have no satisfactory outcome, because 

 the printed descriptions of rock sequences 

 are not sufliciently complete for the pur- 

 pose ; and the closet study of geology is 

 peculiarly exposed to the perils of hobby- 

 riding. A student of the time problem can- 

 not be sure of a .persistent, equable sedi- 

 mentary rhythm without direct observation 

 of the characters of the repeated layers. He 

 needs to avail himself of every opportunity 

 to study the series in its horizontal extent, 

 and he should view the local problem of 

 original versus imposed rhythm with the aid 

 of all the light which the field evidence can 

 cast on the conditions of sedimentation. 



Neither do I think of rhythm seeking as 

 a pursuit to absorb the whole time and en- 

 ergy of an individual and be followed 

 steadily to a conclusion ; but hope rather 

 that it may receive the incidental and oc- 

 casional attention of many of my colleagues 

 of the hammer, as other errands lead them, 

 among clififs of bedded rocks. If my 

 suggestion should succeed in adding a 

 working hypothesis or point of view to the 

 equipment of field geologists, I should feel 

 that the search had been begun in the 

 most promising and advantageous manner. 

 For not only would the subject of rhythms 

 and their interpretations be advanced by 

 reactions from multifarious individual ex- 

 periences, but the stimulus of another hy- 

 pothesis would lead to the discovery of un- 

 expected meanings in stratigraphic detail. 



It is one of the fortunate qualities of 

 scientific research that its incidental and 

 unanticipated results are not infrequently 

 of equal or even greater value than those 

 directly sought. Indeed, if it were not so 



there would be no utilitarian harvest from 

 the cultivation of the field of pure science. 

 In advocating the adoption of a new point 

 of view from which to peer into the mysteri- 

 ous past, I would not be understood to adr 

 vise the abandonment of old standpoints, 

 but rather to emulate the surveyor, who 

 makes measurement to inaccessible points 

 by means of bearings from different sides. 

 Every independent bearing on the earth's 

 beginning is a check on other bearings, and 

 it is through the study of discrepancies that 

 we are to discover the refractions by which 

 our lines of sight are warped and twisted. 

 The three principal lines we have now pro- 

 jected into the abyss of time miss one 

 another altogether, so that there is no point 

 of intersection. If any of them is straight, 

 both the others are hopelessly crooked. If 

 we would succeed we should not only take 

 new bearings from each discovered point of 

 vantage, but strive in every way to discover 

 the sources of error in the bearings we have 

 already attempted. 



G. K. GrILBEET. 



THE EIGHTH GROUP OF THE PERIODIC SYS- 

 TEM AND S03IE OF ITS PROBLEMS* 

 I. 

 In the early work of Newlands and of 

 Mendeleefif, which subsequently developed 

 into the periodic law, a serious difiScuIty 

 was met with in dealing with iron, cobalt, 

 nickel, and the metals of the platinum 

 group. In Newlands' modified statement 

 of his law of octaves he says: "The num- 

 bers of analogous elements, when not consecu- 

 tive, differ by seven or by some multiple of 

 seven." Thus we find him grouping f cobalt 

 and nickel under a single number ; so rho- 

 dium and ruthenium ; so also platinum and 

 iridium. Cobalt, nickel, palladium, plati- 



*Addres8 by the Vice-President and Chairman of 

 Section C, American Association for the Advance- 

 ment ot Science, June, 1900. 



t Cliem. Neios, 13, 130 (1866). 



