On the Measurement of the Specific Gi'avity of Liquids. 113 



is not large when compared with their other constituents, and 

 the proportion of that substance which is thus added to the soil 

 must be small, still plants may during their growth, as in the 

 case of the alkaline and earthy salts, take up a considerable 

 quantity of this substance, though its proportion in the soil may 

 be but very small. Further, as arsenic is well known to be an 

 accumulative poison, by the continued use of vegetables contain- 

 ing even a minute proportion of arsenic, that substance may col- 

 lect in the system till its amount may exercise an injurious effect 

 on the health of man and animals. 



As connected with this subject, I may observe that I was in- 

 formed of a curious fact, — that sheep did not appear to like Mr. 

 Rathbone's turnips which were grown with superphosphate, so 

 well as those where the ordinary farm-yard manure had been 

 employed, and that they could not be made to eat enough of the 

 former turnips to fatten them properly. If this was really the 

 case, it would api)ear to favour in some degree my views as to 

 the probable unwholesomeness of vegetables grown with manures 

 containing even in small quantities so deadly a poison as arsenic, 

 which my experiments have shown that plants are capable of 

 taking up from such manures. 



Finally, these investigations appear to have a medico-legal 

 bearing; for in cases of suspected poisoning by arsenic, where 

 the evidence may chiefly depend on the detection of a small 

 quantity of that substance in the liver and other viscera, as is 

 sometimes the case, my experiments would tend to throw much 

 doubt and uncertainty on such cases, because the presence of a 

 minute quantity of arsenic in the viscera may not be owing to 

 its direct administration, but to its having found its way into 

 the system through the vegetable and, indirectly, animal food 

 taken by the individual. 



These and other important considerations connected with this 

 subject can only be determined by a series of carefully conducted 

 experiments, which 1 purpose commencing, and I hope at some 

 future time to have the pleasure of communicating their results 

 to this Society. 



XXI. O-n the influence of Capillary Attraction upon the Hydro- 

 metrical Measurement of the Specific Gravity of Liquids. By 

 Cn. Langbeuo, late Professor of Natural Philosophy at 

 Christiania*. 



IN order to test the accuracy of an hydrometer, you may 

 cither immerse it in various test-spirits of known alcoholic 

 strength, or you may adopt frisson's method, which, as is known, 

 * From I'og(;cn(loift"'s Anniilcn, vol. cvi. j). 2'jy. 



PMl. Mar/. S. 4. Vol. 18. No. 118. Aut/. 1851). I 



