384 



Anniversary Meeting. 



[Nov. 30, 



practice to award one for the mathematical and physical, and the 

 other for the biological sciences. 



One of these medals has this year been awarded to Professor Peter 

 Guthrie Tait, for his various mathematical and physical researches. 



Professor Tait is well known for his numerous and important 

 papers in both pure mathematics and physics. The late Sir William 

 Hamilton regarded him as his own successor in carrying on and 

 completing the newly invented calculus of quaternions, of which 

 Professor Tait is continually making new applications. Among his 

 investigations in the domain of experimental physics may be men- 

 tioned his determination of the conducting powers of metals for heat 

 by a method which appears to possess special advantages, and his 

 investigation of the effect of extremely great pressures on ther- 

 mometers, undertaken with a view to deducing correct results for 

 the temperatures at great depths in the ocean from the observations 

 made in the " Challenger " expedition. This latter subject has led 

 him to investigate the behaviour, as to compressibility and develop- 

 ment of heat, of liquids and solids under enormous pressures, a 

 subject in which he is still engaged. Before concluding I must 

 mention his elaborate papers on systems of knots, recently printed in 

 the Transactions of the Royal Society of Edinburgh. 



The other Royal Medal has been awarded to our Fellow, Mr. Francis 

 Gal ton, for his statistical inquiries into biological phenomena. 



Mr. Galton is well known as an explorer and geographer, and his 

 mind is singularly fertile in the devising of ingenious instruments 

 for various objects. Many years ago he brought before us some 

 remarkable experiments instituted with a view to test a particular 

 biological theory, in which rabbits of a pure variety were so con- 

 nected with others of a different variety that the same blood cir- 

 culated through both individuals, and the point to determine was 

 whether this blood-relationship, in the most literal sense of the term, 

 had any effect on the offspring. Contrary to what the theory in 

 question led us to regard as the more probable, the result proved to be 

 negative. It is, however, in accordance with the rules for the award 

 of the Royal Medals, more especially the later investigations of 

 Mr. Galton, in relation to vital statistics, that have been taken as the 

 ground of the award. He has shown that by taking the average of a 

 number of individuals having some condition in common, indivi- 

 dual peculiarities apart from that condition are eliminated in the 

 mean, and results are obtained which may be regarded as typical of 

 that condition. One way of doing this is by his method of compound 

 photographs. Thus we may obtain typical features of criminals of a 

 particular kind, of consumptive persons, and so forth. By adhering 

 to the method of averages, he has even succeeded in obtaining a 

 mathematical expression, very closely verified by observation, con- 



