^it? New Inftrument for Mine hoting. 



The author remarks, i, that the two pieces of the inftrument being conne£led to- 

 gether, it can eafily be let down into any hole, and drawn up again ; 2, that if the 

 lower piece refts on a fixed fupport, the upper piece is capable of defceuding through 

 a quantity determined by the fpace left in the excavation, which receives the two 

 keys in ^ ^ ; and that during this defcent, the knives will be forced afunder by the cone 

 of the lower piece forcing itfelf between their backs; 3, that the upper piece is capabla 

 of turning upon the lower, in which cafe the knives will cut away the ground, and the 

 fragments will fall into the groove, and be conduced into the cup beneath ; 4, laftly, 

 that if the inftrument be drawn up again, the two knives will retire into their cells, 

 cither by the efFe£l of their own elafticity, or by that of a fpring properly placed 

 'for that purpofe, or by the re-aAion of the ground itfelf, which prefles them as 

 they rife. 



The author aftorwards enters more at large into the ufcs of bis inftrument, which 

 ftie reporter of the fociety concifely ftates as being effe£led by adapting to the in- 

 "ftrument a feries of rods fuccelEvely lowered into the cavity, and of which the length 

 is fuch that the knives of the inftrument fliall be found at theexaft height of the ftratum 

 intended to be examined when the loweft rod touches the bottom. Other rods are of 

 courfe to be added above, in order to conduit and manage the inftrument ; in this 

 tituation of things nothing more is required than to turn the apparatus in the fame 

 manner as a borer, and when it is prefumed that the knives have detached a fufficient 

 quantity, the inftrument is drawn up. 



The author terminates his memoir by feveral eflential obfervations. The firft 

 relates to the neceftity of not leaving the upper rods to the a<Sion of their own weight, 

 •which would produce the great inconvenience of feparating the knives too much 

 at firft, and endangering the upper rods by too great refiftancc. The rods may 

 eafily be lowered properly, and by degrees, by employing the frame and fcrew a, 

 ■fig. 2, through which the lipper rod pafles. 



The fecond obfervation relates to the different methods of adjufting the verifier 

 to the precife height where the action is intended to take place. For this purpofe 

 a rod of the proper length may be forged, in order that it may be fixed to one or 

 more of the common rods ; or otherwife the operator may provide himfelf with two rods 

 of one decimetre, one of two decimetres, and another of five decimetres,, which fyftem 

 •will give all the lengths from decimetre to decimetre, from 1 to 9, &c.- 



The third and laft obfervation relates to the depth of the circular cut which 

 the two knives will make. Under like circimiftances a cavity of twice the dimenfrons 

 may be made with one knife inftcad of two. The Cngle knife muft h.we the form- 

 xeprefented in fig. a. 



