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In the fecond of thefe publications, Mr. Henry in a proper and fpirited manner defends his moral character, and the justice and accuracy of his experiments, against the imputations and animadverfions of Dr. Glafs. He accufes that gentleman of having, in the foregoing pamphlet, rafhly and wantonly traduced a reputation as fpotlefs as his own; and produces the refpectable teftimonies of Dr Percival and Mr. Aikin in his behalf, which are as favourable to his character as a man, as they are decifive in verifying his experiments above objected to by Dr. Glafs. Some of these were performed in the presence of the fift of thefe gentlemen, and were afterwards repeated by him, and ftill more fully and accurately by Mr. Aikin. The experiments of the latter particularly are by him declared to have been made with the greatest care and attention; and those of both were attended with fimilar refults to thofe indicated by Mr. Henry in his Strictures.'


Dr. Glafs, in his Examination,' lays great ftrefs on the fuperior and unequalled lightnefs' of his brother's magnefia, and produces an experiment to prove that Mr. Henry's preparation is one-third heavier than the amazing light magnefia, now fold under the name of Mr. Glafs.' This circumftance alone, in his opinion, fufficiently proves the fuperior purity of the lat ter: as magnefia is lighter than any of the known absorbent earths or neutral falts; and therefore the purer it is, or the less quantity there is of these heavier fubftances mixed with it, it muft neceffarily be proportionally lighter.

Mr. Henry appears to us to have been always folicitous to acquire this property for his magnefia, and to have met with fome difficulty in the attempt. In anfwer to Dr. Glafs however, and in defence of his veracity against a particular charge of the Doctor's, he declares that on filling a pill box with fome of his own magnesia, and afterwards with fome prepared by Mr. Glafs, which was procured in 1771, and fome of which he has now by him, his own magnefia was found to be lighter than the latter; weighing only 3 fcruples 17 grains, whereas Mr. Glafs's weighed 4 fcruples and 4 grains.

That levity, cæteris paribus, may afford a prefumption in favour of the purity of magnefia, is not to be denied; but we cannot readily agree with the learned Examiner that the trying the specific gravity of two different parcels of magnefia affords an accurate, much lefs a fole, or fufficient teft of their relative purity though the purity of metals, and the ftrength of inflammable fpirits may thus be precifely afcertained. The levity of magnefia appears to depend, in a great meafure, on certain minutia in the conducting of the procefs, which are extrinfical to, or do not affect, the goodness or purity of the pre



paration. The late Mr. Glafs, in his pamphlet on this fubject, obferves p. 13, that the refult of the procefs is at one time a powder very fubtil and extremely light; and, at another, when the operation has been repeated with a variation fcarce diftinguishable, the product has been a very ponderous powder, and fometimes even a substance not inferior in hardness and closenefs of texture to a flone.

As Mr. Henry feems, by his filence at leaft, partly to acquiefce in Dr. Glafs's doctrine on this fubject, we fhall endeavour to fhew, in a familiar way, that the fuperior purity of magnefia cannot be fufficiently afcertained by its fpecific gravity; to which Dr. Glafs however affirms that it is exactly proportioned.' He found that the fpecific gravity of Glafs's magnefia is to that of Henry's nearly as 2 to 3; and it appears from a table of the fpecific gravities of magnefia, chalk, and other bodies, given in the third of thefe pamphlets, or the Refutation,' that a fpecimen of Henry's magnefia was found to be nearly of double the fpecific gravity of Glafs's*. In one fpecimen of Henry's preparation we have found it even to exceed that proportion, while it fully ftood every other known chemical teft of purity, as did likewife the fpecimen of the Proprietor's magnesia with which it was thus ftatically compared.

Now it appears from the table abovementioned that this light magnesia of Mr. Glafs's might, for example, bear to have a fixth part of its bulk of chalk added to it, or a quarter of its bulk of crabs' claws; or even fo large a portion as a third of its bulk of flacked lime mixed with it; and yet the magnefia, thus grossly adulterated, would by the proposed fatical test be found fpecifically lighter than the fpecimen of Henry's magnefia laft mentioned, in which nevertheless no impurities could be detected by the nicest chemical tests. In fhort, it is evident that, if specific gravity is folely or principally to be attended to, in determining the purity of magnefia, no lefs a quantity than a third, or a half, or more of Henry's magnefia (fuppofing Glass's to be perfectly pure) muft confift in irely of impurities :-a fuppofition too abfurd to be admitted: for how can it be fupposed that fuch a load of impurity can lie concealed in it, and clude every nicer chemical criterion;-open only to detection. through the fingle medium of a pair of scales ?

In the third of thefe publications, or the Refutation,' the ponderofity of Mr. Henry's magnesia is still further infisted upon,

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as a matter of reproach; and the levity of the Proprietor's magnefia is held up, as being univerfally admitted to be the moft unquestionable teft of purity.' The other allegations in favour of this preparation are, that its fpecific gravity is almoft invariably the fame, as is the lofs of weight which it fuftains by calcination:-circumstances which clearly prove that it is always prepared according to a certain invariable ftandard, namely that of purity; whereas Mr. Henry's magnefia has no fuch ftandard different parcels, calcined and uncalcined, varying confiderably in this particular.

A fet of experiments on the two rival magnefias is likewife given, which were made under the infpection of Dr. Smith, Dr. Vivian, Dr. Parfons, and Dr. Wall, in the univerfity of Oxford. From thefe experiments we collect that neither of thefe preparations, when calcined, was rendered cauftic, or gave water the taste of lime; but it is obferved that, on impregnating with fixed air the water in which Henry's calcined magnefia had been infufed, a perceptible fediment was found at the bottom of the glafs the day after the experiment had been performed whereas no precipitation could be perceived, either at the time, or ever afterwards, in the water, impregnated with fixed air, in which Glafs's magnefia had been digefted. Farther, Glafs's magnefia, both calcined and uncalcined, is faid to have been more readily and perfectly diffolved in the vitriolic acid, than Mr. Henry's preparation.-Thefe experiments certainly prove that the prefent Proprietor can make pure magnelia.

These are the moft material, though not the most obfervable parts of this performance, which contains the moft illiberal and indecent reflections on the character of Mr. Henry; who is reprefented and treated in it as an unprincipled intruder on what the Author feems, fomewhat mistakenly in our opinion, to confider as his freehold, in confequence only of a private transaction between him and the late Mr. Glafs. In one place Mr. Henry's • veracity,' is faid to be as light as his magnefia is heavy,' and in other parts of it, he is reprefented as fcandalmfly' invading the Author's property; and as meanly and criminally attempting to gratify his avarice, or relieve his neceffities, at the expence of the Proprietor's reputation and fortune; and, in fhort, is charged with a want of every principle of integrity.'-To justify fuch Janguage as this, the moft" damning proofs" would scarcely be fufficient. We can find however, no fuch proofs, or even prefumptions, in either of thefe productions. Such grofs abufe muft indifpofe every liberal mind against the caufe which it is employed to fupport; when they reflect to what kind of treatment an honeft man is liable to be expofed, for giving useful information to the Public, whenever fuch information tends to disturb a proprietor in the quiet enjoyment of the sweets of a lucrative monopoly.



ART. X. Nature ftudied with a View to preferve and reftore Health, &c. With an Account of a most powerful and fafe Deobftruent Medicine, &c. By William Smith, M. D. 8vo. 4 s. Owen. 1774. ND can this be the Dr. William Smith, who has formerly been fo often the object of our animadverfion, both in jeft and earnest, on the various fubjects of Religion, Metaphyfics, Government, and, more particularly, Medicine ?— If it be, we profefs we scarce know our old acquaintance againhe is fo altered :-Nil fuit unquam tam difpar fibi. That Dr. Smith, we all remember, was a moft violent ftickler for the certainty of medical theory, and the omnipotence of phyfic; declaring that we had even an intuitive knowledge of the caufes of difeafes,' and that the phyfician might always accomplish a cure, if he properly discharged his duty. On the contrary, we find the prefent Dr. William Smith grievously lamenting the fallacy of medical theory, and the uncertainty of phyfic;' declaring it to be an art which is not yet fixed upon the eftablished principles of fcience,' and affirming that the human fpecies would certainly enjoy a greater fhare of health, if there were fewer phyficians, and lefs phyfic.'

Our old acquaintance feemed to have a particular affection to the apothecary's fhop, and publifhed a large quarto, comprehending not only all the trash at prefent to be found in it, but filled with many loads of the rubbish that has long fince been swept out of it; pointing out likewife, with fingular diligence, the fuperlative virtues of each article, with all the credulity and confidence of a Lady Bountiful; and terminating each chapter of the work with a long and goodly train of fourscore or a hundred recipes t. The prefent Sofia, on the contrary, declares in an elegant figure, that the Apothecary's hop is, in his opinion, the worst difeafe the human body is fubject to;' and afterwards, in a vein of not the moft cleanly pleafantry, tells us that fome patients are fo very extravagant in their demands, that they have no opinion of their phyfician, except he' -(the patient, we fhould fuppote-not the poor doctor furely) goes through the whole exercife of fhitting, piffing, fpewing, fweating, bleeding, bliftering, &c.' He adds, that the phyficians who would willingly difabufe people concerning their credulity about phyfic, dare not do it left they should lofe all their practice; and is afterwards even fo grofs as to hold up to us the picture of a patient attended by a phyfician and an apothecary, as that of a poor innocent victim crucified between two thieves.'



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* See M. Review, October 1768, page 316, and October 1 page 281.


†M. Review, September 1769, page 194.


How is a poor unenlightened Reviewer to reconcile thefe Bagrant contradictions, which are no where explained or accounted for in this performance ?-efpecially when he is fatisfied, from the internal marks he observes in this work, in which likewife many paffages occur that he recollects to have read in the Author's former publications, that this is really the production, of the original Dr. William Smith, and not of a counterfeit.When the vain fit is upon us, we fometimes fatter ourselves that our former good-humoured and well-intended ftrictures on the Doctor's unbounded confidence in the intuitive certainty of phyfic, and on his credulity with regard to the fuperlative powers of the moft paltry drugs, may have contributed to this ftriking change of principles and practice :-but that, as generally happens to your new converts, the first zeal of reformation has carried our new Catechumen to thefe unwarrantable lengths.Not content, like Martin †, difcreetly and deliberately to strip off the fuperfluous trimmings and tinfel from the coat; he fuddenly falls a ripping and tearing, like Jack, sends them all to the devil, and in his rage rends the main body of the garment from top to bottom.

Not to plume ourselves however too confidently on the fuppofed efficacy of our former repeated admonitions, which is nowhere acknowledged in the prefent volume ;-perhaps a circumftance that occurs in the work will fufficiently account for the Doctor's now differing fo much from his former felf. Towards the latter part of it, it appears that he has made a difcovery of a particular compofition, that will nearly fuperfede the ufe of all other medicines, and render the apothecary's fhop a ufelefs nuifance. As little occafion too will there now be for medical theories, as for drugs, when the Public is in poffeffion of this fafe and very powerful medicine, which opens the most minute obftructions'-and has not yet failed in any cafe where it has been administered, which has been moftly when other means have been tried in vain, and in difeafes commonly thought incurable ;'-particularly in confumptions, afthmas, fevers, both putrid, malignant, and inflammatory, palfies, king's evil, in all cutaneous difcafes, and all ulcers external and internal, in the rheumatifm, and even, he has good reafon to believe,' in the gout. In fhort, it is fuch an acquifition to the art of healing, as will be more valued the more it is known.'



It is a powder, it seems, and the most powerful deobftruent,' fays the Doctor, which, I believe, Nature ever produced.'Nature however, though fhe undoubtedly must have had fome hand in this affair, must allow Art to have had a very confiderable share in the economy and fabrication of this powerful pro

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