"RECENT ADVANCES" 227 



form of a course of lectures which Tait gave by request to a company of 

 some ninety Edinburgh citizens, mostly professional men. The lectures were 

 delivered in his usual style from the briefest notes, and the book was compiled 

 from the verbatim shorthand report. Of all Tail's published works it gives 

 the best idea of his method as a lecturer. One of its greatest merits to a real 

 student of the subject is the exposition of Carnot's Principle. The name of 

 Carnot was first introduced in Lecture IV on the Transformation of Energy, 

 and occurred again and again throughout the succeeding chapter on The 

 Transformation of Heat into Work. The story goes that when Tait began 

 the Sixth Lecture with the words " I shall commence this afternoon by taking 

 a few further consequences of the grand ideas of Carnot," an elderly pupil 

 sitting towards the back was heard to protest vehemently against the name 

 of Carnot. 



The published book contains thirteen lectures, but some of the lectures 

 delivered were not published. I remember for example being one of a few 

 undergraduates who were allowed to join the class on two of the occasions 

 on which it met in the University. This change of meeting-place was for 

 the sake of the experimental illustrations, which could not well be performed 

 in an ordinary hall. These two lectures on the Polarisation of Light and 

 Radiant Heat do not appear in the volume, probably because much of the 

 subject matter could not be regarded as recent in the sense in which the 

 doctrine of energy was recent. 



In addition to the clear exposition of the foundations of the modern theory 

 of energy, Tait gave in these lectures an admirable account of the physical 

 basis of spectrum analysis and the first great discoveries made by Kirchhoff 

 and Bunsen, and by Huggins, Lockyer, Young and others. Astrophysics is 

 now a branch of astronomy claiming its own specialists and possessing its 

 own literature ; but, in the seventies, solar and stellar spectroscopy was but a 

 particular illustration of the broad principle of spectrum analysis. Another 

 important section of Recent Advances was devoted to the discussion of the 

 atom and molecule, their magnitudes and masses, and even their ultimate 

 constitution. 



The book was reviewed in all our best papers and journals at considerable 

 length, in general with high commendation. The following quotation from an 

 article in the Quarterly Review, Vol. 142, entitled " Modern Philosophers on 

 the Probable Age of the Earth " may be taken as a good type of the appreci- 

 ative notices which abounded. 



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