the sudden Expansion of compressed elastic Fluids. 25 1 



Some of these results agreeing, and some being at variance* 

 with those exhibited in figs. 2. & 3, I constructed the follow- 

 ing apparatus for the purpose of examining more distmctly 

 the effects produced by the expansion of compressed air under 

 similar circumstances. A (fig. 4-.) is a longitudinal section of 

 a perpendicular pipe of four 

 inches internal diameter, con- 

 nected with a reservoir of com- 

 pressed atmospheric air. BC 

 is a cross section of a flat cir- 

 cular piece of wood 1 1*8 inches 

 in diameter, having a circular 

 orifice four inches diameter 

 through its centre, and adapt- 

 ed to the upper end of A, so 

 that this orifice shall coincide 

 with the interior circumference 

 of A. DE is the section of 

 another flat circular piece of 

 wood, of the same diameter as 

 BC, and placed directly over 

 it, and fixed so that it may be 

 uniformly depressed or raised 

 from BC by means of screws. 

 F is an inverted glass syphon 

 inserted into the centre of DE, 

 and G is a similar syphon in- 

 serted into DE, at the distance 

 of 1-5 inch from F. H, I, and K are three small glass tubes, 

 open at both ends, inserted into BC, and havmg their lower 

 ends immersed in a trough L of coloured water. 1 he centre 

 of the tube H was at the distance of -9 mch; that of 1, 2-1, 

 and that of K, 3-4 inches from the interior side of A. Ihe 

 space between BC and DE being adjusted to -2 of an inch, 

 some mercury being put into all the inverted syphons, and 

 the compressing apparatus being set to work,— the syphons (j 

 and M indicated each an interior pressure of 1-25 inch, and 

 the svphon F, 1 -3 inch of mercury. The coloured water rose 

 9- inches in H, 2- inches in I, and -5 inch in K. On the 

 interior pressure in A being increased, the coloured water 

 rose higher, in nearly the same proi)ortion, in H, Ij |i"" ^; 

 and the amount of the downward pressure on DE still much 

 exceeded that of the upward pressure Irom A. 



Some of these results being still at variance with some ot 



those described in the article of the Annaks dc Chumc already 



nuoted, 1 prevailed on Mr. Dalton to witness a repetition ol 



' 2 K 2 the 



