[7] 



DIRECTIONS FOR COLLECTING ROCKS MERRILL, 



be necessary, or at least desirable, to visit the locality again. More- 

 over, tlie mode of occurrence of a rock mass is often a matter of primary 

 importance. Do not trust to small labels gummed to the specimen. 



If, in the museum or laboratory, it is found desirable to fix a number 

 upon a specimen in order to insure it against loss or displacement, the 

 following method, as pursued in the i^ational Museum installation, may 

 be found advisable: A blue rectangular strip of sufficient size to 

 receive the number is painted upon the specimen in oil colors, the 

 material used being dry ultramarine blue mixed with ordinary white 

 lead and sufficient hard oil finish to thin it for applying with a brush. 

 This dries quickly, giving a firm, glossy surface, upon which the num- 

 ber is then painted in 

 white — Windsor and 

 Newton's flake- white 

 tube paints, thinned 

 with turpentine, having 

 been found best fitted 

 for the purpose. This 

 gives a practically inde- 

 structible number, suffi- 

 ciently conspicuous to 

 be readily found on spec- 

 imens of any color or 

 texture, and which, if 

 neatly done, does not in 

 the least mar their ap- 

 pearance (fig. 7). The 

 method is of course ap- 

 plicable only to sub- 

 stances of considerable 

 firmness of texture. 



In collecting the larger 

 materials illustrative of 

 dynamic phenomena, 

 only very general direc- 

 tions can be given, since each individual case requires separate treat- 

 ment. The size and shape of the specimen must depend on what it is 

 intended to illustrate, and the means of getting it out and transporting. 

 If blasting must be resorted to, use ordinary slow-burning blasting 

 powder, which lifts but does not shatter; never resort to dynamite. 

 Here, too, care must be taken not to deface by scarring the faces 

 intended for exhibition. Many a fine block has been spoiled through 

 lack of attention to this rule. Never deface a specimen by painting 

 the address upon it for shipment. In these days of dry plates and 

 films it is frequently advisable to photograph an outcrop from which 

 the specimens are selected; this to show other structural features 

 than those brought out by the specimen, as well as to serve as an aid 

 to the future identification of the locality. 



Fig. 9.— Collecting bag or knapsack. 



