PROFESSOR CHRISTISON ON THE ACTION OF WATER UPON LEAD. 269 



white shining incrustation, and the surface of the water was covered with a film 

 of similar appearance. On inquiry, he learned that the water always presented 

 this appearance after being exposed for some time, but that it was quite transpa- 

 rent when first drawn ; and he afterwards personally verified these facts. 



Being well aware of the action of water on lead, and of the consequences of 

 the insidious introduction of the compounds of that metal into the human body, 

 Mr JOHNSTON, with much discernment, although he had never seen a case of lead- 

 colic before, was strongly inclined to believe that he had to deal with that dis- 

 ease. He suspended his ultimate decision, however, until he had an opportunity 

 of examining chemically the substance deposited by the water. This he found to 

 be soluble in weak acetic acid ; and the solution gave a white precipitate with 

 sulphuric acid, a white one with carbonate of potash, a yellow one with iodide of 

 potassium, and a black one with sulphuretted hydrogen. The last test, an ex- 

 tremely delicate one, likewise made the water itself brown. As these results 

 left no doubt Avhatever of the presence of lead in the water, he could as little 

 entertain any doubt of the nature of the housekeeper's illness. She Avas treated 

 accordingly, recovered slowly but steadily, and in October was quite well. She 

 had resided in the house, and constantly used the water for eight months before 

 her final severe illness ; but for some months previous to that attack, she had 

 been often annoyed with stomach-complaints and constipation. Her niece, a girl 

 of twelve, who had been residing with her for a few weeks only, was also attacked 

 Avith these premonitory symptoms of lead-colic ; but she soon recovered under 

 Mr JOHNSTON'S care. No other person had resided for any length of time at the 

 Lodge during the period in question. LORD ABERDEEN had been there with some 

 friends for a feAv days only. 



Mr JOHNSTON, Avith Avhose approbation, as well as the sanction of LORD ABER- 

 DEEN, the facts of this incident are made public, consulted me respecting it about 

 the middle of September, and aftenvards communicated much additional infor- 

 mation, partly, indeed, in reply to suggestions made by me. The folloAving is a 

 short narrative of the Avhole particulars. The Avater Avas first introduced into the 

 house in the summer of 1840, by a lead-pipe from a spring at the distance of 

 rather more than half a mile. The spring Avas purchased for the purpose, as it 

 had been represented to be of fine quality ; and an analysis, by a chemist in 

 the neighbourhood, appeared to sheAV that it was of unusual purity, and contained 

 very little saline matter. This will presently be seen to be by no means the 

 case. 



The pipe had been in use for several months before the housekeeper went to 

 reside at the Lodge. When Mr JOHNSTON first examined the water, it had been 

 in constant use for twelve months. And yet it continued to impregnate itself 

 with lead to the last : In the water, Avhen fresh draAvn, he could detect lead by 

 sulphuretted-hydrogen eA r en without concentrating it. 



VOL. XV. PART II. 4 D 



