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might be al $ o procured in a pure and isolated gaseous form ; and , after several unsuccessful trials , he succeeded , by heating a mixture of quicklime and sal ammoniac , when a great quantity of air escaped , permanent over quicksilver , but , like the acid gases , rapidly absorbed by water .
The odour of this gas was pungent in the extreme , and it possessed the property of salvolatile , smelling salts , and similar substances , of turning vegetable blues to green . After several experiments , in which the
absorbing powers of different substances in regard to this air , were tried , Dr . Priestley became impatient to discover the effect of mixing it with the acid airs just described , —he imagined that he should form a neutral air .
On putting this notion , however , to the proof of experiment , he was surprised to observe , that when marine acid air , and the volatile alcaline air , were mixed in due proportions , they were wholfy condensed into a solid . And with sulphureous air a very similar result was afforded .
Dr . Priestley concluded that alcaline air was considerably lighter than acid air , because , on mixing them over mercury , he observed the former to float above the latter ; on putting a lighted candle into alcaline air the flame was enlarged , and a portion of the air appeared to burn with flame .
We have now considered the principal discoveries of Dr . Priestley , upon which his title to originality rests , and it must be allowed that they are not less important than numerous . If we even consider them merely as insulated tlicts , they are of a very superior character , and tended greatly to
enlarge our knowledge of the chemical elements of matter ; but the new views of many natural and artificial phenomena , which they exposed , and which before were buried in deep obscurity , confer upon them a more exalted aspect , and have obtained for them the deserved meed of
universal admiration . In perusing Dr . Priestley ' s tracts , we find the thread of the narrative occasionally knotted with conceit , and weakened by garrulity ; but these blemishes are ecftnpensated by prevailing * candour and perspicuity of style : he had greatly extended the boundaries of science , and was awake to the impor-
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tance of his conquests ; but resisted that febrile thirst of innovation and reform , which was endemic amoilg contemporary chemists . " At present , ' * says he , in the Preface to his third volume of JExpwiments and Observations , relating to various branches of Natural
Philosophy , " At present all our systems are in a remarkable manner unhinged by the discovery of a multiplicity of facts , to which it appears difficult or impossible to adjust them : we need not , however , give ourselves much concern on this account , For , when a sufficient number of new facts shall
be discovered , towards which even imperfect hypotheses will contribute , a more general theory wiil soon present itself , and , perhaps , to the most -incurious and least sagacious -eye . Thus , when able navigators have , with great labour and judgment , steered towards an undiscovered
country , a common sailor , placed at the mast head , may happen to get the first sight of land . JLet us not , however , contend about merit , but let us all be intent on forwarding the common enterprise , and equally enjoy any progress we may make towards succeeding in it , and , above all , let us
acknowledge the guidance of that great Being , who has put a spirit in man , and whose inspiration giveth him understanding . " With this quotation , sufficiently characteristic of his general style , I shall take leave of Dr . Priestley , and introduce another hero of chemical history , his contemporary and great rival , Scheele .
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ilfr . Brmsby on the Character of Dr . Bentley . 683
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Dudley , Sib , November 5 , 1818 . IT affords me great pleasure to be able fully "to vindicate the character of Dr . Bentley , from the very severe charge brought against him by Mr .
llutt , in the last number of the Monthly Repository [ pp . 624 , 6 £ 5 ~ ] . I have before me , bound up with several tracts on the same subject , by Bentley Swift , Addenbrooke , Whiston , and others , a copy of Collins ' s ' * Discourse
of Free-thinking , " in 8 vo . The first leaf is unhappily lost , and there are no means of ascertaining the date of the impression . At the 90 th page , & passage of Victor is quoted from MilFa Prolegomena , and it is thus translated by Collins : ' In the consulship of
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Citation
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Monthly Repository (1806-1838) and Unitarian Chronicle (1832-1833), Nov. 2, 1818, page 683, in the Nineteenth-Century Serials Edition (2008; 2018) ncse.ac.uk/periodicals/mruc/issues/vm2-ncseproduct2482/page/19/
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