June 9, 1916] 



SCIENCE 



819 



tative routine. There is also a gain in quan- 

 titative discipline because, for example, tiie 

 drill in combining weights includes the usual 

 quantitative determination of silver as chlo- 

 ride and the volumetric work illustrating oxi- 

 dation and reduction simplifies much of the 

 quantitative course to foUow. 



A semester of this course is to be followed 

 by quantitative analysis proper with stress on 

 the illustration of principles. 



To give this second-year course profitably 

 the last three months of general chemistry 

 should be devoted — in the laboratory — to the 

 simplest possible system of qualitative anal- 

 ysis taught without much use of physical 

 chemistry. I have used such a system for sev- 

 eral years and find that it pays. The gain here 

 is in teaching the student classification, com- 

 parison, logic, showing him a focus for the 

 many isolated facts he had accumulated and 

 which had begun to tire him. There is also a 

 certain craft on the part of the teacher using 

 this plan, for there are few first-year students 

 not roused to enthusiasm by qualitative work. 

 Many remain in the department for advanced 

 courses who would otherwise have lost inter- 

 est. Yet no time is wasted, for such a founda- 

 tion makes possible the second-year course 

 outlined above. The majority of every class in 

 elementary chemistry do not go on to advanced 

 chemistry. This plan gives them a more 

 rounded training. 



Better a genuine system than attempts to 

 popularize the subject by imrelated tests of 

 foods. The student has a right to a proper 

 mental discipline even though he does not al- 

 ways insist upon that right. 



Haert N. Holmes 



Oberlin College 



stylolites in quartzite 

 To THE Editor of Soienoe: Dr. F. L. Ean- 

 some describes and figures what he calls " !Nat- 

 ■urally Etched Quartzite " in his report on the 

 Geology and Ore Deposits of the Breckenridge 

 District, Colo.^ While conducting a field 

 course in geology from the University of Mis- 



iF. L. Eansome, TJ. S. G. S., P. P. 75, pp. 

 36-37, and plate 31. 



souri in this area during the summer of 1915, 

 the writer observed these so-called etched sur- 

 faces and interpreted them in the same way as 

 Dr. Eansome had done, until one of the stu- 

 dents brought in to camp a piece of the 

 quartzite with a new structure. This was 

 immediately recognized as a fragment of a 

 stylolite. The writer investigated the locality 

 at once, as he had been studying this particular 

 structure in limestone for a number of years 

 and was much interested in such an unusual 

 mode of occurrence. 



The locality where the stylolite was found 

 was near where the 10,500-foot contour line 

 crosses the small area of Dakota quartzite to 

 the northeast of Lincoln in French Gulch. 

 This slope is covered with masses of quartzite 

 boulders. The study of a few specimens soon 

 revealed the fact that the so-called etched sur- 

 faces were the exposed ends of stylolites, a 

 type of surface the writer was very familiar 

 with from his Study of stylolites in limestone. 

 The very rough pitted surface produced by 

 the stylolitic rods is well shown in Fig. 1 on 

 plate 31 of Dr. Eansome's memoir. The 

 depth of the depressions depends upon the 

 length of the stylolitic columns which are 

 rarely over one and three quarter inches in the 

 quartzite, the majority being less than one 

 inch (between one fourth and five eighths of an 

 inch). When the stylolitic columns are short 

 the pits are shallow and well rounded. Since 

 the plane near the end of the stylolitic zone is 

 a plane of weakness the majority of the frac- 

 tures of the rock are along these planes, thus 

 accounting for the abundance of the pitted 

 surfaces among the quartzite boulders. The 

 writer collected a series of specimens showing 

 all gradations between stylolites and the so- 

 called etched surfaces. Many specimens were 

 collected which show the depressions still oc- 

 cupied by part of a stylolitic column, the frac- 

 ture having occurred along the plane near the 

 end of the columns rather than having fol- 

 lowed the irregular line of contact of the 

 stylolites. After the fractured surface has 

 been exposed to the weather these ends are 

 loosened and fall out, thus leaving the depres- 

 sions. In some specimens the stylolites can be 



