1820.] the Rev. Dr. Hales. 169 



conflagration would pass. This method was carried to Constan- 

 tinople, and enabled the Turks to save one of the finest buildings 

 in that Ottoman capital. 



Two years before this he had given a method of injecting into 

 the abdomen in the case of paracentesis any injection wished for 

 during the very time that the dropsical liquor is passing off. 

 He had been told that a woman labouring under an ascites had 

 been cured by her surgeon by means of an injection of red wine 

 and alum water. This piece of information led him to think of 

 a method of improving the process. His method was exceed- 

 ingly simple. Two trocars were introduced into the abdomen 

 instead of one ; and while the liquid of dropsy was running out 

 of one canula, the injection was to be introduced through the 

 other. This process has been for many years very much 

 employed in hydrocele, and with the best effects. Its success 

 in ascites is much more problematical. 



The phenomena of electricity had attracted the attention of 

 men of science during Dr. Hales's hfe time ; and in the latter 

 j)eriod of his existence, they had acquired a very high degree of 

 celebrity, and were become the fashionable study. It was not 

 hkely that they could escape the attention of a man possessed of 

 the curiosity and the sagacity which characterized Dr. Hales. 

 Accordingly we find a paper by him on electricity in the Philo- 

 sophical Transactions. He remarks that the colour of the electric 

 spark is different when drawn from iron, from copper, and from 

 an egg laid upon copper. Hence he infers that the substance 

 from which the electric spark comes furnishes some part of its 

 own substance to the spark, and thereby occasions tlie peculiar- 

 ity of colour. 



Earthquakes were particularly common and dreadful in their 

 effects during the life time of our philosopher. Hence his atten- 

 tion was naturally called to them, and his ingenuity employed, 

 in attempting to account for their existence. He conceived he 

 had found an explanation in an experiment which had been 

 related in his Statical Essays. He had obtained a quantity of 

 nitrous gas by dissolving iron pyrites in nitric acid, and he found 

 that when this gas was mixed with conmion air, it became red, 

 and the bulk of the mixture was diminished by a volume nearly 

 equal to the original volume of the nitrous gas. This experi- 

 ment, which was very imperfectly understood by Dr. Hales, and 

 indeed was not fully explained till many years after his death, he 

 employed to account for the origin of earthquakes. The nitrous 

 gas he considered as an air impregnated with, or consisting of, 

 sulphureous vapours. These vapours in his opinion were conti- 

 nually exhaling from the earth. When they were produced in 

 great quantities, and came to be mixed with pure air, the vacuum 

 formed by the sudden destruction of the elasticity of so great a 

 quantity of air would, in his opinion, be sufficient to occasion 

 earthquakes. Notwithstanding the wildiiess of this hypothesis, 



