A Simplified Technique for Forensic Precipitation Tests.

novement of the end of the bar (e) and assures a quick and positive movement of the valve when the vessel (d) moves from the "down" to the "up" position. A suitable counter weight is suspended from the bar (e). As indicated in the diagram, when the vessel (d) is in the "up" position air pressure from the compressed air main forces the culture solution up into the sand containers. As the solution rises in the sand it also rises in tube (b), the height of which is adjusted so that when the solution has almost reached the surface of the sand it overflows and fills vessel (a) until the siphon (c) is started. Vessel (a) then empties into vessel (d) where the weight of solution overcomes the balance weight, causing the rotation of the valve (g), shutting off the compressed air and releasing the air pressure in the carboy. The culture solution from the sand containers drains back into the carboy, while the one-way glass valve in the tube (f) allows the culture solution in the vessel (d) to drain back into the carboy. By constricting this tube the frequency of irrigation can be adjusted. When vessel (d) has emptied it returns to the "up" position and in so doing again turns on the compressed air at the valve (g). Other sand containers irrigated from the same carboy are attached to the solution line (b) as indicated at (i). When additional culture solutions are to be used their carboys need only be connected to the air line, as shown at (j). Carboys need not be of the same size, but it is essential that the amount of solution in each carboy be so adjusted that when the compressed air is automatically shut off the level of the residual solution in all carboys is the same. T. B. LOTT DOMINION LABORATORY OF PLANT PATHOLOGY, SUMMERLAND, B. C.