transverse hole in the plug 24 or other attachment means as desired the secondary weight 64 is optional as indicated by its illustration in broken lines in fig2 a and 2b the secondary weight 64 serves to increase the total density of the apparatus 10 and attached weight 64 when the apparatus is used in a well or borehole containing a relatively dense liquid and or to increase the rate of descent through a fluid in the borehole at this point the apparatus 10 is positioned at the desired predetermined depth in the borehole or well with the tracer agent or other material still sealed within the inner cylinder 12 the tracer agent is released by a weight 68 that is disposed concentrically along the suspension line 62 while the weight 68 is illustrated as a frustoconical solid in the drawings the shape or configuration of the weight 68 is not critical so long as it possesses sufficient mass to actuate the apparatus 10 as described below larger and or more streamlined weights may be incorporated as desired the weight 68 remains at the surface as the apparatus 10 is lowered into the borehole or well once the apparatus 10 is positioned at the desired depth the weight 68 is dropped and it slides down the line 62 when the weight 68 strikes the top wall 34 of the outer cylinder 14 it jars or displaces the outer cylinder 14 downward around the inner cylinder 12 which cannot move vertically due to its attachment to the suspension line 62 the outer cylinder 14 is displaced downward by the force of the weight 68 until its top wall 34 strikes the upper edge of the top extension 18 of the.