PLAYFAIR. 93 



decided predilection for science had hitherto made him hesitate 

 about engaging in a vocation, the duties of which, he felt, if con- 

 scientiously discharged, would necessarily interfere greatly with 

 the studies he was loath to abandon. In this emergency, however, 

 he considered himself no longer entitled to indulge in these predi- 

 lections, and therefore made an application, which proved successful, 

 to Lord Gray, the patron, for a presentation to the livings of Liff 

 and Benvie, which had been previously held by his father. From 

 this period until 1782, he was constantly resident at Liff, occupied 

 almost exclusively with the pastoral duties of his office, and with 

 the education of his younger brothers. 



In the year 1779 Playfair contributed to the 'Transactions' of the 

 Royal Society of London a paper on the ' Arithmetic of Impossible 

 Quantities,' which exhibits, within a very small compass, a striking 

 example of the rare and admirable talent of detaching the sound 

 spirit of science from what may be termed its mysticism. In the 

 year 1782 he was induced by very advantageous offers to resign his 

 charge, and to superintend the education of Ferguson of Raith, and 

 his brother Sir Ronald ; an arrangement which restored him in a 

 great measure to the literary and scientific society of Edinburgh, 

 and enabled him to visit London, where he was gratified by a 

 personal introduction to several of the most eminent cultivators of 

 science in that city. 



Playfair was received into the University of Edinburgh during 

 the course of the year 1785, and, in consequence of an arrangement 

 made between Dr. Adam Ferguson and Mr. Dugald Stewart, was 

 appointed joint-professor of mathematics with Dr. Ferguson, whose 

 delicate state of health prevented him from discharging the active 

 duties of the professorship ; Mr. Stewart filling the chair of moral 

 philosophy, previously held by Dr. Ferguson. 



Previous to this, like Leslie, Playfair had been twice a candidate 

 for a similar honour, but unsuccessfully. On the first occasion, 

 when only eighteen years old, he had offered himself, with the 

 approbation of his instructors at St. Andrew's, as candidate for the 

 professorship of mathematics in Marischal College, Aberdeen, and 

 had sustained with much credit a competitive examination which 

 lasted eleven days, and embraced nearly the whole range of the 

 exact sciences. Out of six competitors, two only were judged to 

 have surpassed him the Rev. Dr. Trail, who was appointed to the 

 office, and Dr. Hamilton, who afterwards succeeded to and long 

 filled it with much reputation. 



In 1788, Playfair published, in the 'Transactions' of the Royal 

 Society of Edinburgh, a biographical account of Dr. Matthew 

 Stewart, which also contains a singularly clear and interesting 

 account of the labours of Dr. Simson in the restoration of ancient 

 geometry. In this year likewise appeared his paper ' On the Causes 

 which affect the accuracy of Barometrical Measurements,' which is 



