174 ANNUAL OP SCIENTIFIC DISCOVERY. 



to measure the volume of water displaced; and his method is applicable to 

 any other liquid, as alcohol, benzine, etc., since it is only with volumes, and 

 not weights, that the calculations are made. 



Three different modifications of this principle arc in use, of which we give 

 the outline. One is to fill a test-tube, which forms a straight cylinder, and is 

 graduated, with a liquid in which the substance to be examined is insoluble, 

 to note the height of the liquid, and to Aveigh the whole. The substance, in 

 coarse powder, is next thrown in, the height of the fluid again noted, and 

 the whole re-weighed. The two notations and weighings give the data to 

 determine the specific gravity. 



The second mode is especially adapted for bodies which, on account of 

 size or shape, cannot be introduced into a graduated cylinder. A strip of 

 wood, through which is stuck a. pin, blackened at the point, is laid over a 

 beaker-glass, which is then filled with water until the surface of the latter 

 just touches the point of the pin. After introducing the substance, the water 

 is drawn up into a graduated pipette until reduced to the same level, even 

 with the point of the pin. The volume of the water measured in the pipette 

 shows that of the substance. 



The third moclifi cation is intended for technical purposes more particularly. 

 The apparatus consists of a half-gallon glass cylinder, provided with a 

 tubulus at the lower end, through which passes, on the outside, a bent glass 

 tube to about half the height of the cylinder, where it is bent at two right 

 angles, ending in a fine opening, beneath which is afterwards placed a grad- 

 uated cylinder. Water is poured into the large cylinder until it commences 

 to run from the fine opening; when this ceases, the graduated cylinder is 

 put in its place, and the substance, previously weighed, gently introduced 

 into the large vessel. The water rises, and the quantity corresponding to the 

 volume displaced will run from the glass tube and be measured in the grad- 

 uated cylinder. We may here notice a mode of determining the speciiic 

 gravity of such substances as potatoes, which is in general use among the 

 potato distillers of Northern Germany, to guide them in the valuation of 

 the percentage of starch, which stands in some proportion to the specific 

 gravity of the potato. A saturated solution of common salt is prepared, 

 and the potatoes placed in it; they will swim on top until the density of the 

 salt liquor is reduced by Avater, Avhich is added until they are suspended in 

 the solution, but do not sink to the bottom. The specific gravity of the 

 diluted solution is then taken Avith a common areometer, and is the same as 

 that of the potatoes. 



JAPANESE SCIENCE. 



A recent correspondent from Japan describes an ingenious method practised 

 in that country for getting Avater from the bottom of a deep lake. For this 

 purpose a cone-shaped earthenware bottle Avas employed, having a hole at its 

 apex and a A^ery small one at the broad part, Avhich Avas stopped by a gum 

 soluble in Avater. The bottle was then sunk, apex downwards, by means of 

 a Aveight and a line, and alloAved to remain about a quarter of an hour at the 

 bottom of the lake, by which time the gum was dissolved and entrance for 

 the Avater obtained, the air being forced out through a little hole at the 

 bottom. It Avas then drawn up, and the hole at the bottom plugged Avith a 

 tiny Avooden peg. 



