Crawford, Adair (DNB00)

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CRAWFORD, ADAIR (1748–1795), physician and chemist, born in 1748, was a pupil at St. George's Hospital. After he had obtained his M.D. degree he is said to have practised with great success in London, and for so young a man was surrounded by a large circle of attached friends. Through their influence he was eventually appointed one of the physicians to St. Thomas's Hospital, and elected as professor of chemistry to the Military Academy at Woolwich.

At the age of twenty-eight Crawford visited Scotland. The experiments which he made on heat imply that he was for some time in Glasgow and in Edinburgh. Crawford informs us that he began his experiments in Glasgow on animal heat and combustion in the summer of 1777. They were communicated in the autumn of that year to Drs. Irvine and Reid and to Mr. Wilson. In the beginning of the ensuing session they were made known to the professors and students of the university of Edinburgh, and in the course of the winter they were explained by the author, to the Royal Medical Society of that city. In 1779 the first edition of Crawford's work was published in London by Murray. The full title of his book was ‘Experiments and Observations on Animal Heat, and the Inflammation of Combustible Bodies; being an attempt to resolve these phenomena into a general law of nature.’ In this work he examined all the opinions of Huxham, Haller, Heberden, Fordyce, and others. He submitted to Priestley, who was an especial friend, his experimental examinations of blood in fever. Priestley considered them to be very complete, and Crawford's deductions satisfactory. Crawford's book, ‘Experiments,’ attracted considerable attention, and William Hey, F.R.S., surgeon to the General Infirmary of Leeds, published in 1779 ‘Observations on the Blood,’ in which he expressed his approval of Crawford's views. In 1781 William Morgan published ‘An Examination of Dr. Crawford's Theory of Heat and Combustion,’ in which he urged sundry objections to his conclusions; as did also Magellan in his ‘Essai sur la nouvelle théorie du feu élémentaire,’ &c. In 1788 Crawford published a second edition of this work, in which he candidly informs us that a very careful repetition of his experiments had revealed many mistakes respecting the quantities of heat contained in the permanently elastic fluids. ‘In an attempt,’ he says, ‘to determine the relations which take place between such subtle principles as air and fire we can only hope for an approximation to the truth.’ In 1781 the severe criticism of his theories led Crawford to discontinue his physical inquiries and devote his attention more directly to strictly professional matters.

He was distinguished by his desire to be accurate in all his investigations. All his pieces of apparatus were graduated with a delicate minuteness which has never been surpassed. His experiments were invariably well devised and carried out with the most rigid care, the accuracy of his apparatus being constantly tested by all the methods at the disposal of the chemists of his day. Among his especial friends and counsellors were Black and Irvine, and of these he writes: ‘I have endeavoured to mark, with as much fidelity and accuracy as possible, the improvements which were made by Dr. Black and Dr. Irvine in the doctrine of heat before I began to pay attention to this subject.’ He admits to the full his indebtedness to these chemists. So closely did he follow in the path indicated by Black and Irvine that he tells us ‘it has been insinuated that I published in a former edition of this work a part of the discoveries made without acknowledging the author. This charge was completely answered by a letter written from Glasgow College 27 Jan. 1780 by Dr. Irvine, in which he says: ‘I likewise lay no claim to the general fact concerning the increase or diminution of the absolute heat of bodies in consequence of the separation or addition of phlogiston which is contained in your book.’

The investigations prosecuted by the philosophers of this period were vitiated by their acceptance of the ‘Phlogistic Theory’ of Stahl and Beccher, which involved the inquiry into the phenomena of heat in a mist of hypothetical causes. Crawford's ‘Experiments and Observations’ clearly exhibit his sense of the difficulties surrounding the doctrine of phlogiston, which he admits ‘has been called in question.’ Kirwan, to whom Crawford dedicated his book, was the first to suggest that phlogiston was no other substance than hydrogen gas; but it was reserved for Lavoisier, in 1786, to extinguish the Stahlian error. Crawford failed to realise the truth which was so near him. He determined, however, the specific heats of many substances, both solid and liquid, and his investigations upon animal heat led Priestley to his admirable investigations.

In 1790 Crawford published a treatise ‘On the matter of Cancer and on the Aerial Fluids,’ and a considerable time after his death, i.e. in 1817, Alexander Crawford edited a noticeable book, by his relative, bearing the title of ‘An Experimental Inquiry into the Effects of Tonics and other Medicinal Substances on the Cohesion of Animal Fibre.’ Dr. Adair Crawford attracted the attention of his medical brethren by being the first to recommend the muriate of baryta (barii chloridum) for the cure of scrofula. This salt is said to have been given in some cases with success, but prolonged experience has proved that the use of it is apt to occasion sickness and loss of power. Crawford, when only forty-six years of age, retired on account of delicate health to a seat belonging to the Marquis of Lansdowne at Lymington, Hampshire, and there he died in July 1795. A friend who knew him well wrote of him as ‘a man who possessed a heart replete with goodness and benevolence and a mind ardent in the pursuit of science. All who knew him must lament that aught should perturb his philosophical placidity and shorten a life devoted to usefulness and discovery.’

[Kirwan's Defence of the Doctrine of Phlogiston; Scheele's Experiments on Air and Fire; De Luc's Treatise on Meteorology; Dionysius Lardner's Treatise on Heat; Sir John Herschel's Natural Philosophy; The Georgian Era, iii. 494; Gent. Mag. vol. lxv.; Watt's Bibl. Brit.]

R. H-t.