REFLECTING LEVEL AMD GONIOMETER. 



239 



found to be peculiarly useful in our thin, horizontal, and varying 

 fossiliferous strata, where at one point we find a seam, say an 

 inch thick, filled with trilobites, at another a similar seam, abound- 

 ing with entrochites, &c. It is evident, that by two straight strips, 

 the one to be used as a radius, and the other as a chord, divided 

 into degrees, we may convert the above instrument into a goni- 

 ometer for measuring angles either of elevation or of depression. 

 This level is to be adjusted by the usual method of reversal, but 

 it needs an assistant to observe the bubbie in the reverse position. 

 In observing, the operator may hold the level at arm's end 

 like a pistol, or he may bring one of the sights close to his eye, 

 so as to divide the pupil, according as he finds it most agreeable. 

 Mr. Davis, No. 11 Cornhill, Boston, will manufacture the re- 

 flecting level above described, at the very moderate price of two 

 dollars. 



LOCKE'S LEVEL. 



I'iff. 1 -« 



Fig. 1. 

 » s. A common spirit level, 

 o a. A reflector. 



b. A strip of brass bent round, soldered to the tube, and bearing the pivots 

 J J, which permit the reflector to be folded dow^n upon the tube. 

 Fifj. 2. Front View of the Reflector. 

 R. The reflector. 

 T. The tube of the level. 

 //. The pivots. 

 0. An opening underneath the Reflector. 



