7 i2 THE POPULAR SCIENCE MONTHLY. 



and which, though it has been in constant daily use for more than 

 twenty years, is as true and serviceable as ever. 



If at any time the geologist has occasion to lighten his equipment 

 for some long mountain-expedition, where every additional ounce of 

 weight begins to tell by the end of the day, and where, therefore, for 

 the sake of doing as much and holding out as long as possible, he 

 should carry nothing that is not absolutely needful for his purpose, 

 he may advantageously combine the pocket-compass and clinometer 

 in the one instrument to which I have already alluded. This con- 

 venient instrument is about the size of an ordinary gold watch. It 

 consists of a thin, round, flat, metal case, shaped like that of a watch, 

 and covered either with a common watch-glass, or, still better, with a 

 flat disk of strong glass. Instead of figures for the hours and min- 

 utes, the white enameled face of this geological watch is that of a 

 common pocket-compass. But the interval between each of the four 

 cardinal points is divided into 90. On the central pivot, just under- 

 neath the needle, a small brass pendulum is placed, and a straight- 

 edge of metal is soldered on one side of the outer rim of the watch- 

 case in such a position that the instrument will stand on it if need be, 

 and the pendulum will then point to zero. A simple piece of mechan- 

 ism passing through the handle enables the observer to throw the nee- 

 dle off the pivot, or let it down, as he may require. 



As it is impossible for a field-geologist to remember the details of 

 all the observations he makes on the ground, or to insert them on a 

 map, he regards a good note-book as an essential part of his appara- 

 tus. From the nature of his work, he has frequently occasion to make 

 rough sections, or diagrams, and, if possessed of the power of sketch- 

 ing, he has abundant opportunity of aiding the progress of his re- 

 searches by jotting down the outlines of some cliff", mountain, or land- 

 scape. Hence, his note-book should not be a mere pocket memoran- 

 dum-book. A convenient size, uniting the uses of a common note-book 

 and a sketch-book, is seven inches long by four and a quarter inches 

 broad. Let me remark, in passing, that perhaps no accomplishment 

 will be found so xiseful by the field-geologist as a power of rapid and 

 effective sketching from Nature. If he has this power in any degree, 

 he ought sedulously to cultivate it. Even though he may never pro- 

 duce a picture, he can catch and store up in his note-book impressions 

 and outlines which no mere descriptions could recall, and which may 

 be of the highest value in his subsequent field-work. This is true of 

 ordinary detailed surveys, and still more of rapid reconnaissances, 

 which may have their ultimate usefulness enormously increased if the 

 observer can seize with his pencil and carry away the forms of surface 

 as well as the geological relations of the region through which his 

 traverse lies. 



As every device which saves labor and time in the field, or which 

 adds to the clearness of the work, is deserving of attention, I would 



