260 Mr. Meikle on an improved Syphon- Hydrometer. 



can be made, so much the better ; even using, perhaps, for the 

 shorter columns the mere capillary elevations. 



In transparent liquors, we may make the one pair of co- 

 lumns A and W to be depressions under the surfaces of the 

 liquids contained in glass cisterns ; which may be effected by 

 immersing the instrument with the hole previously stopped to 

 confine the air. The depths of the depressions, when in- 

 creased respectively by x and y, should, like the former co- 

 lumns, be inversely as the specific gravities of the liquids. 

 Consequently the required specific gravity becomes 



W-(-x w-x W +■ w 



A-f y ' " a-y ' A + a ' 



which, as the numbers may be larger, is likely to be more ac- 

 curate than the former. For in this case we obtain the spe- 

 cific gravity by dividing the sum of the elevation and depres- 

 sion of the water by the sum of those of the other fluids 



There is still another case in which all the columns may be 

 depressions, and which obviously makes the specific gravity 



W -f x w -\- x W—tv 



~ A +V ' " + y " ' A-a' 



where the rule is the same as in the first case. I may remark, 

 that in all the cases, we might use in place of one of the pairs 

 of columns, the mere capillary elevations, with proper signs. 



As a hole may be apt to weaken a glass tube, especially at 

 the curved part where it should be strongest; two straight 

 pieces of glass tube may be joined, as I have done, by means 

 of a bit of bent tin-tube. The hole may then be more easily 

 made, and will be less apt to weaken the instrument. The legs 

 of the syphon should be graduated or divided into small equal 

 parts. This may be very easily done by merely transferring 

 to the tubes, with the assistance of a square, the divisions which 

 are already made on any scale of small equal parts. It is ob- 

 vious that the legs ought to be parallel. 



Nearly allied to the syphon-hydrometer, is a more complex 

 instrument, called a pump-areometer. It is so named, from 

 its being furnished with a pump at its upper part for exhaust- 

 ing the air to induce the liquids to rise. The requisite de-. 

 gree of exhaustion, however, is so very trifling, that it may be 

 effected, were it in the least necessary, by merely sucking with 

 the mouth at the orifice of a stopcock attached to the top of 

 a syphon. Henry Meikle. 



XLVI. A new 



