216 On a Remarkable Structural Appearance in Phosphorus. 



daring the oscillations of the barometer, until at length the tops 

 of the sticks of phosphorus became exposed. Slow combustion 

 would then set in, the resulting acid would go into solution, and 

 small quantities of fresh air would stream in to supply the par- 

 tial vacuum, and so continue the action. During a falling ba- 

 rometer nitrogen and moisture would stream out of the jar, the 

 level of the water would be again slightly lowered, and a fresh 

 portion of phosphorus be exposed to the attacks of the next 

 portion of oxygen drawn in. In this way by very slow degrees 

 the liquid would be lowered and fresh portions of phosphorus 

 exposed. Those already out of the water would be attacked by 

 every ingress of air, and thus being acted on not only more ener- 

 getically, but also for a longer time than the lower portions, 

 they w r ould necessarily have a conical shape. Moreover the air 

 that streamed into the jar would gradually lose its oxygen in 

 descending, so that the lower portions would be acted on less 

 strongly than the upper. The phosphoric acids as generated 

 would also pass into solution with a certain rise of temperature 

 and a certain expansion of the nitrogen left in the jar. As this 

 cooled down, a little more air would be drawn in, and combus- 

 tion and solution would go on as before. But the most ener- 

 getic action would take place when under a falling barometer a 

 quantity of moist nitrogen streamed out of the jar, and during a 

 rising barometer a fresh supply of atmospheric air streamed in, as 

 already explained. 



Secondly, as to the spiral markings. These cannot have been 

 formed by any action that took place in the jar ; but they show, 

 1 think, the new and interesting fact that the curves which the 

 theory of hydraulics assigns to liquids flowing from an ori- 

 fice, and producing the vena contracta, actually form part of the 

 structure of a body suddenly arrested in its flow by being made 

 solid. 



It is well known that in the ordinary manufacture phosphorus 

 is formed into sticks by being made to flow from a head or re- 

 servoir of the molten element along a short pipe or ajoutage 

 into cold water ; or, rather, as soon as the stick of phosphorus 

 begins to emerge from the warm ajoutage and shows itself in 

 the cold bath, it is seized by hand and cut off at intervals, or 

 drawn out by machinery into a continuous length, so that from 

 15 to 20 lbs. and upwards of phosphorus can be moulded in less 

 than a quarter of an hour. 



Now, of course, in the flow of the molten phosphorus Torri- 

 cellr's theorem applies, viz. that particles of fluid on escaping 

 from an orifice possess the same velocity as if they had fallen 

 freely in vacuo from a height equal to that of the fluid-surface 

 above the centre of the oriflcc. If the head of phosphorus were 



