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nor useful , and I shall rather , therefore , deviate a little on this point , than cloud the perspicuity of my narrative , or crami > it by chronological strictness .
Dr . Priestley ' s character was of so composite an order as to defy brief description or superficial delineation ; he was a politician , a divine , a metaphysician and a philosopher ; and in each of these callings he displayed abilities of a peculiar and occasionally
exalted description . His copious and important contributions to chemical science are the more surprising , when it is remembered that his philosophical pursuits were merely resorted to as a relaxation in his theological studies ; that his mind-was under the
constant agitation of controversy and dispute ; that he was too impatient for deep research , and too hasty for premeditated plans . But , with all these bars against him , he was a
thriving wooer of science : he made more of his time than any person of whom J ever read or beard ; and possessed the happy and rare talent of passing from study to amusement , and from
amusement to study , without occasioning any retrograde movement in the train arid connexion of his thoughts . There is another important feature in Dr . Priestley ' s character , which may tend to throw some light upon his controversy with the French school :
he possessed the strictest literary and scientific honesty ; he makes frequent mention of his predecessors and contemporaries , and enumerates the ideas which he borrowed from them , and the experiments they suggested with more than necessary accuracy and minuteness . His attachment to
chemistry seems to have been formed at Leeds , about the year 1768 , and between that period and the year 1772 he had added several new and highly important facts to the science , which are detailed in a long communication presented to the Royal Society in the spring of that year . It is here that
he relates those researches respecting the influence of vegetation upon the atmosphere , which led to entirely new views of the physiology of plants , and which displayed , in a striking light , some of those masterly and beneficent adjustments of nature , by which the different members of the creation are
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made to minister to each other ' s wants , and thus preserve that eternal harmony which marks the natural world .
As combustion and respiration were connected with the deterioration of air , it occurred to Dr . Priestley to ascertain how far the growth of vegetables might be productive of similar effects .
" One might have imagined , * ' says he , " that since common air is necessary to vegetable as well as to animal life , both plants and animals would affect it in the same manner ; and I own 1 had that expectation when I first put a sprig of mint into a glass
jar , standing inverted in a vessel of water ; but when it had continued growing there for some months , I found that the air would neither extinguish a candle , nor was it at all inconvenient to a mouse which I put into it . "
In experiments of this kind , Dr . Priestley points out the necessity of often withdrawing the dead and dying leaves , lest , by their putrefaction , they . should injure the air : lie also hints
at the noxious powers of some plants , especially the cabbage , of which he kept a leaf in a glass of air for one night only , and in the morning a candle would not burn in it .
Dr . Priestley also extended his experiments to the influence of plants upon air vitiated by animal respiration and by combustion , and found that they in general did not only not contaminate the air , but that they actually restored to purity that which
had been rendered impure by flame and breathing ; and by shewing that this change was effected by groundsel as perfectly as by mint , proved it independent of the aromatic oil to which some in their ignorance had been willing to refer it .
1 hat actual vegetation was necessary , and the mere vegetable insufficient , he proved by exposing the pulled leaves of a mint plant to air , which were unproductive of the regeneration effected by the growing sprig .
Dr . Priestley concluded from these experiments , that the noxious air resulting from combustion , and from the breathing of the different animal tribes , formed part of the nourishment of plants ; and that the purity ' of our
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Mr . Brandes Estimate of Dr . Priestley s Chemical Discoveries . Of ?
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Citation
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Monthly Repository (1806-1838) and Unitarian Chronicle (1832-1833), Nov. 2, 1818, page 677, in the Nineteenth-Century Serials Edition (2008; 2018) ncse.ac.uk/periodicals/mruc/issues/vm2-ncseproduct2482/page/13/
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