H4 Poison of the Viper:x—Corrosive Sullimate.—Vegetation. 
a false estimate of its merits. Such is literally a portraiture of 
the character of the opposition made to the introduction of the 
safety-lamp. I submit it to the liberal and enlightened mind, 
whether it would not have begn more philosophical to have first 
_proved whether this instrument, introduced with such important 
recommendatious, was really so wondrously endowed, and then 
to have given their opinion on its value or demetits? 
Having paid considerable attention to the action of vegetable 
and animal poisons on the system,—the article which appeared 
in your penultimate Number, On the Poison of the Viper, could 
not fail to interest me. I have long believed that azimal poisons 
could be received into the system without injury, and that to 
produce their proper effect they must be introduced into éhe cir- 
culation. The conclusions of the paper in question are beauti- 
fully corroborated by the following extract from a letter to me, 
by Mr. Campbell, the African traveller: “ The Hottentots be- 
lieve, that if they swallow the serpent’s bag of poison, a sting or 
bite from: a serpent will do them no harm. Several of my 
Hottentots assured me they had done it ;—one, who asserted it, 
was a Christian, who I think would hive sooner submitted to 
have been torn to pieces by a tigers than to have uttered a deli- 
herate lie; so I fully credit it.’ 
The article in Dr. Thomson’s Annals for last month, On the 
Test for corrosive Sublimate, &c. calls to my mind a very ex- 
cellent and delicate one for the detection of mercurial salts — 
Rub a little corrosive sa!t or calomel on a piece of silver, or suf- 
fer a drop of a solution of muriate of mercury to rest upon it ; 
a stain of a coppery colour will be left, and this, after a very 
high degree of dilution. 
If I might be permitted to remark on Mr. Tatum’s Experi- 
ments on Vegetation, I would say that they are liable to as many 
and as great. objections as any other that I have seen detailed. 
They were subjected to a confined instead of a free atmosphere, 
and to mercurial etfluvia—the temperature of the included me- 
dium was unnatural, and they would be excluded from those 
thousand sources of vicissitude which constitute the spring of all 
their beauty. I shall still hold unchanged the opinion I have 
long maintained as the result of direct experiment ; namely, that 
the quantity of carbonic acid evolved by plants will bear but a 
pitiful proportion to the floods of oxygen poured out upon the 
-atmosphere by the exercise of the vegetative functions—My 
mind therefore rests contented on the experiments of Priestley 
and Ingenhousz since corroborated, in contradiction to those of 
Ellis and Tatum. These observations will receive additional 
weight from the following deductions. It is notorious that oxy- 
gen is evolved from plants during the stimulus of light, and that 
: vegetation, 
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