SIMPLE EUDXOMETttIC APPARATUS. ^J 



above it in proportion to its whole height, in the fame manner 

 as if the prelTure were derived in any other way from an equal 

 column of water ; and the cafe is reduced to a perfect analogy 

 with the prefTure of a head of water of this height, fince the 

 air a6is upon the particles entering the tube in the fame man- 

 ner as the water does in more common cafes. Had the refult 

 of the experiment been different, it would have been an ex- 

 ception to the general principle of the prefervalion of living 

 force, or the equality of the potential afcent to the afiual 

 defcent ; for, the water moving with the velocity due to half 

 the height only, would have been capable of afcending but to 

 half the height. 



XI. 



Account of a funple Eudiometric Apparatus conjlruSted and ufed 

 hy Dr. T. C. Hope, F. R. S. Edin. &c. &c. 



^INCE the difcovery of the uncertainty with which the ap- The uncertainty 

 plication of nitrous gas to atmofpheric air, and other mixtures ^^^"^'"'"^^'■•caJ 

 containing oxigen is attended, it has been found defirable to w1t"nkrousgae 

 prefent folid or liquid fubftances for the abforption of that prin- renders the ule 

 ciple. This on firft confideration may feem at leaft as eafy to ^.g^^gj^jj^^gf^ 

 be done as to mix two gafes ; but it is by no means fo, becaufe 'ary, 

 the liquids in particular poffefs a degree of chemical adivity 

 which readers it inconvenient to imraerfe the hands in them, 

 or to expofe their furface to the open air. Dr. Hope, whom 

 I had lately the pleafure of feeing in town, mentioned an ap- 

 paratus he ufes in his ledures and experiments, which is at 

 once fimple and effedual, and I am happy in his permiffion to 

 defcribe it in this place. 



A Fig. 3. Plate IV. reprefents a bottle which may be I i Apparatus by 

 inch in diameter, and 2|- inches in length, having a neck and ^e^a'^^ifgd to"" 

 Hopper at D, and another neck, as ufual at C, into which laft without incon- 

 the neck of the bottle or body B, is fitted by grinding. This "''^"ience. 

 lafl: was made of the fame diameter as the bottle, but feven or 

 eight inches long. B contains the gas, and A the liquid; for 

 example, folution of hydrofulphuret. When B is thus con- 

 nedted with A, the compound veflel may be inverted and agi- 

 4- tated : 



