466 Scientific Proceedings^ Royal Dublin Society. 



The apparatus (fig. 1) is made up of a piece of galvanized gun-barrel 

 steam tubing F, three inches in diameter and seven and a-half inches long. 

 Tlie lower end is closed by an end plug-cap ^screwed on to it. Above the cap 

 is a disc of thick iron K', which gives a good hold for the bolt attached to tlie 

 channel iron L. To the upper end an elbow-piece D is screwed to give 

 attachment to a cross-pin acting as a fulcrum C of the lever A. The corner 

 is cut off obliquely to allow free movement to the lever. A piston E is 

 pivoted to the lever by a shackle and bolt B two inches from the fulcrum. 

 The piston rests on the mass of swelling seeds P, and actuates the lever. 

 Just above tlie plug the gun-barrel cylinder is pierced by the tube H 

 admitting water. A second similarly placed tube facilitates cleaning. A 

 strong metal grating G, supported by three stout legs (one of which is figured 

 at M), rests on the plug and serves to allow the free passage of water upwards 

 to the seeds. On the grating rests a piece of wire gauze, on top of which is 

 placed a layer N (about lialf an inch deep) of fine gravel. Sand is placed 

 over the gravel, and on this the seeds, mixed with a certain portion of fine 

 sand, are carefully packed. 



The sand serves a double purpose : it fills up the spaces between the seeds, 

 and so limits their power of free-swelling movement ; and, secondly, it 

 permits the easy passage of water throughout the mass, so that all seeds are 

 uniformly and continuously wetted. Even when registering the maximum 

 pressure, a head of a few inches causes the water to pass through the mass of 

 seeds and sand. A piece of channel steel L is bolted on to the bottom plug 

 K and strengthened by an angular strut bolted to the lower part of the 

 elbow-piece {D). It carries at the distal end a screw-hook, which serves 

 for the lower attachment of the spring balance, the upper end of which is 

 secured to the lever. 



The lever is a steel bar an inch and a-half wide, a quarter inch thick, and 

 six and a-half feet long. The free end of the lever is pierced by a drill- 

 hole six feet from the fulcrum. Through this hole the spring balance can be 

 attached by means of a bolt. The balance used registered up to two hundred 

 pounds, but was not nearly powerful enough, since in order to record the 

 maximum pressure we had to use an inconveniently long leverage (6 feet). 

 If we were making another instrument, we should use smaller bore gun- 

 barrel, as a pressure of fifty atmospheres which we registered from peas in 

 the sensitive instrument would lift the three-inch piston with a force of 

 5260 pounds, or over two tons. Even the one and a-half inch steel lever was 

 bent on its edge, also an inch H -steel girder, which was originally used as the 

 base or fixed arm, in place of the channel steel. 



We found it advantageous to select a balance which gave as little 

 extension as possible in proportion to the reading. 



