134 DETECTION OF ARSENIC. 



but null and void ; and if a soluble salt be generated, as may- 

 be, the humidity of the soil in which the body is interred, 

 may by percolating through the decomposing mass, entirely 

 wash it way. It is scarcely possible to assign limits to the 

 almost infinitely small portion of arsenic, which may be 

 detected by analysis, so accurate and inevitable are the results 

 of chemical science, when skilfully obtained; but great nicety 

 and scrupulous adherence to every rule which it inculcates, 

 are indispensable to the attainment of such results. In 

 this country, unfortunately, we are compelled to depend in 

 great measure upon unpractised hands, except in large cities, 

 and hence, where evidence is submitted to a jury, unless the 

 chemical witness be known to be expert and practised in his 

 profession, his testimony should be received with extreme 

 caution. It has been shown, by what has already been said, 

 that numerous counteracting causes exist, which may deceive 

 the analyst, and in a case to which reference was made in a 

 very early part of this paper, so great was the deception, that 

 all who were convinced by their experiments of the presence 

 of arsenic, were subsequently shewn, by a critical investiga- 

 tion, to have been completely deceived in their results. With 

 this knowledge of the difficulties and responsibilities which 

 environ the chemical witness, in cases where poison has been 

 suspected to have been administered I have endeavoured to 

 shew what his true course is, and how he may avoid those cir- 

 cumstances which lead to false inductions. If I have failed 

 to do this, an apology is due for having so long occupied your 

 time and patience, but if, on the contrary, these remarks have 

 had any tendency to instruct, I shall consider the time occupied 

 in their preparation, exceedingly well spent. They have been 

 compiled, in the few leisure hours which could be snatched 

 from the active pursuits of business, and are doubtless, far less 

 complete than the importance of the subject demands. They 

 may perhaps, however, awaken a spirit of investigation among 

 some who have hitherto not particularly investigated the sub- 

 ject, and as all of us may be called upon, either as witnesses 

 or jurors, in cases where justice demands a rigid scrutiny into 

 the dark designs of some foul murderous spirit, they may serve 

 to prepare our minds for the proper exposure of its weapons, 

 or to the certain expression of a righteous judgment. 



