SCIENCE. 



"Vol. XXI. No. 51I 



te-!tiruony of the studpnt who relies on his microscope and starts 

 out with the idea of subordinating his facts to the answers it may 

 give, or that of the field-observer, who only studies the grander 

 structures and has a predisposition to explain such as the fore- 

 going by referring them to sedimentation, shall here be received 

 with the greater credence." 



The Bulletin here quoted embodies the results of portions of 

 two seasons' field-work, as well as a large amount of labora- 

 tory study of the greenstone schists. However fairly the figures 

 may "present the issues," it is unfortunate for Professor Win- 

 chell's argument that he did not select some of the many similar 

 examples with which his Held experience has made him personally 

 acquainted. The fact is that the two occurrences selected by 

 Professor Winchell from Bulletin No. 63 demonstrated in the field 

 the dynamic origin of their structures so convincingly, that no 

 microscopical examination was ever made of them. It would 

 never have occurred to Professor Winchell or to any other ' Held 

 geologist" to explain the particular features which, in the Bulle- 

 tin, these two figures represent, by sedimentation, if Ihey had 

 observed the natural exposures. A single narrow shear zone, 

 crossing a great wall of massive diabase 60 feet in 1 eiaht, makes 

 it certain, without help from the microscope, that the cblorile 

 schist which borders the zone is the result of the fra.\ing out of 

 the rock by the motion. Nor is there less certainty that the wide 

 gaping gashes in the basic eruptives are due to some mechanical 

 strain. There are cases without number, as every one who has 

 worked in the crystalline schists well knows, where their is doubt 

 as to whether a parallel structure is due to sp'limentatinn or to 

 dynamic metamorphism; but why Professor Winchell should se- 

 lect two cases as clear as these, it is difE<-ult to undersand. In 

 the text descriptive of the original figures, it is plainly stated that 

 the first is unsatisfactory because it represents only a hand-speci- 

 men, whereas the structure, to be appreciated, must be seen on 

 the face of a high rock-wall. In regard to the second figure, it 

 is also stated that it is only a diagramatic representation of an 

 area on the rock-wall about three feet square. If there is diffi- 

 culty in arriving at correct conclusions from the studv of natural 

 exposures, all the more caution is necessary in imerpreiing an- 

 other author's figures, espet;ially when these ate distinctly de- 

 scribed as inadequate. 



In reality, what are known in the Like Superior region as 

 "greenstones" and "greenstone-schists" are not one thing but 

 a great variety of different things. Some of them are :< assive 

 lavas, others accumulations of ash material stratified by sra\ity 

 or water. They possess structures of diverse origin, which may 

 to the field geologist appear very much alike. 'I hcse must I'e 

 studied first and foremost in the field, but to avoid confnson and 

 misinterpretation we need all the hflp available, even from the 

 mioroscope. Here we may see plainly that wli it maoro-copically 

 looks alike is in reality difl'erent In fine, there is i o di-crepaccy 

 between the results of field and laboratory woik, ami \i he who 

 is only a field geologist find his conclusioi s at \ ariame with th -se 

 of a field geologist who is also a student of ilie nucro^cipe. it be- 

 hooves him to revise the-^e conclusions iiefore ne oasts a"-!! e the 

 results of modern petrographic re>earch. 



Absolute 

 measurement! 



WORCESTER SCHOOL CHILDUEN THE GROWTH OF 

 THE BODY, HEAD, AND F.^f'E 



BY GERALD M. WEST, CAMBRIDOE, MASS 



An investigation into the laws goveruui he .,ro 

 parts of the bO'ly was instituted in tlie Wor.-.'.ster 

 spring of 1891, and a short notice of ilip .iiinvi.i i: 

 faces of girls was published in i^cience .luly 3 siiii 

 pose to give a summary of some of I lie n.ii r r ..aU; 



The observations were made in the )ir :jj n iii^ 

 schools, and in two of the private sclmo s in tii ■ ly 

 The number of individuals examined w.is 3,. .'JO, . i\- 

 from 5 to 21 years, The nationaliti.-s were u^,iier< 

 66 per cent were of American parentULi , ,ier c 

 per cent of English and Scotch, and 6 per cent sc ut 



Plate T. contains the curves of growth of the diameters of head 

 and face, with their indices. 



C 1. The maximum length measure'1 from j 



J the glabella. V Head. 



] 2. The maximum breadth. ) 



1 3. The " " of the face. 



("4. The proportion of the breadth of the face to 



I the breadth of the head. 



The proportion of the breadth of the head to 



the length of the head. 

 The proportion of the breadth of the-face to 

 the length of the head. 

 Length of Head (1). — In absolute length we see that the girls' 

 length of head is less than that of the boys throughout its whole 

 period of growth, and consequently throughout life. We find, 

 however, that this difference in length does not remain the same 

 year by year, but varies considerably, being, for example, 3 milli- 

 meters at the ages of 11, 12, and 13, and rising as high as 6 milli- 

 meters before, and 7 millimeters after, that age. We find also 



Indices. -| ' ' 



I 6. 

 I 



that the annual increment is very irregular in both sexes. We 

 have periods of growth alternating with a cessation of growth. 



In girl~ the greatest length of head is reached at about the be- 

 ginning of the eighteenth year. In boys the head continues to 

 grow until at least the age of twenty-one. The period of greatest 

 irregularity in the annual increment seems in the case of girls 

 to he before, in the case of boys after, the eleventh and twelfth 

 years. 



Breadth of Head (3). — The breadth of head presents phenomena 

 very similar to those of the length of head, i e., periods of alternate 

 growth and cessation of growth. The girls' width of head is less 

 than that of the boys, but the difference diminishes markedly about 

 the eleventh year, from this age until the fourteenth year the curves 

 are parallel, then this again becomes more widely seiiarated. The 

 age of maximum width in girls is about seventeen, in boys the 

 maximu'U is not yet reached at the age of twenty one. 



Breadth of Face (3). — Here again we meet with similar phe- 

 nomena; the breadth of face of the girls increasing rapidly with 

 irregular annual increments until the seventeenth year, when the 

 maximum growth is reached. The faces of the boys continue to 

 grow until the eighteenth year and probably beyond. 



