266 New Instrument for Spcclfx Gravities. 



the size of which should be so regulated that the water may not only 

 fill it but rise a few tenths in the tube, observe the height to which it 

 does rise (say 15 tenths.) Reverse the instrument again and when 

 the water has returned into the tube, unscrew the portion ^fgh once 

 more and introduce into the funnel shaped portion of the bottle, a 

 small fragment of the mineral, ^c. whose sp. gr, is required, having 

 previously taken its actual weight in air, which suppose to be 200 

 tenths. Again screwing on the portion of the bottle efgh turn back 

 the instrument to its proper position and unscrewing the top (a) to 

 prevent the reaction of confined air observe how high the water now 

 stands in the tube which suppose to be 115. Now, as before the 

 mineral was inti'oduced, the water stood in the tube at 15, its intro- 

 duction has evidently displ<)iced a column of water, (equal to the 

 hulk of the mineral) weighing 100 tenths of grains or the difference 

 between 115 and 15; but the actual weight of die mineral is 200, 

 consequently its sp. gr. is 200 divided by 100, or twice that of dis- 

 tilled water. 



The water will be observed to fall gradually in the tube when 

 minerals which ahsorb it are under trial ; in this case the greatest 

 height must be taken. 



This instrument is calculated also to shew the sp. gr. of mineral 

 waters or of wines, spirits, oils, &:c. by a comparison of the weight 

 shewn by the tube with the actual weight; thus, if a spirit stands in 

 the tube when reversed at 115 and weighs only 100, its sp. gr. is to 

 that of distilled water as 100 is to 115 or as 869, &c. is to 1.0 ; but 

 1.0 is the sp. gr. o[ distilled water therefore .809, &;c. is the sp- gr. 



of the spirit. 



The actual weight of the spirit may be taken, when it is in the tube, 

 by deducting the weight of the tube, vdthout tlie spirit, from the 

 weight of the tube witli tlie spirit. 



Solid substances also, which float on water, are by this instrument 

 readily weighed, specifically, without attaching any heavier body to 

 them because they must he submerged, that is if they be larger than 

 the orifice of the tube which will of course in that case prevent them 



from rising in it. 



Another advantage peculiar to this method of taking the sp. gr. is, 

 that it is of no importance what description of water is made use of in 

 weighing hydrostatically solid bodies, as the quantity by measure dis- 

 placed will be in all cases the same. To color the water witli some 

 vegetable substance will be found useful. 



^ 



