74 Notices respecting New Books. 



good deal that would be out of place if it occurred in a work intended 

 as a text-book for scientific students. Doubtless many " intelligent 

 persons " listened to these lectures at the Royal Institution, and 

 many more will read them in their present form, with pleasure and 

 profit, who would never have exerted their intelligence for ten 

 minutes in trying to read a more systematic or (as they would pro- 

 bably call it) dry treatise on acoustics. Such a result is one for 

 which Professor Tyndall deserves the thanks, not only of the " in- 

 telligent persons " aforesaid, but also of those who have made science 

 the occupation of their lives. The nature of the service rendered to 

 this latter class by works like the present was so well stated a few 

 months ago at Dundee by Sir William Thomson, while speaking of the 

 author's previous work on "Heat," that we cannot do better than quote 

 his words : — " The scientific world are much indebted to Dr. Tyndall, 

 not merely for his investigations, but for the manner in which he 

 has attracted interest to the results of science, and for the beautifully 

 clear explanations he has given of scientific principles. Scientific 

 men are extremely dependent on the sympathy of the rest of the 

 world ; and this is very largely increased when the illustrations of 

 scientific investigations are made known in a clear and interesting 

 manner, as Dr. Tyndall has made them known, to a very large part 

 of the population of this country and throughout the civilized world." 

 This recognition of the value to science of Dr. Tyndall' s literary 

 labours is in our opinion extremely well deserved, and is as applicable 

 to the work before us as to that to which it originally had reference. 

 Nevertheless it is certain that the interest excited by the magnificent 

 experiments which he exhibits so admirably to his audience at the 

 Royal Institution, and which he describes with such vivacity and 

 graphic power that those who only read of them must feel almost as 

 if they saw them performed, is by no means a sure sign that those 

 who feel it have any deep sympathy with science for its own sake. 

 These experiments are often of such a kind that the least intelligent 

 person, looking upon them merely as beautiful sights, and without 

 any perception of their scientific significance, could not witness them 

 without delight ; but they are to the general truths and reasonings 

 which constitute the real framework of science what the sweetmeats 

 and playthings of childhood are to the solid food and serious occupa- 

 tions of manhood. By this we do not at all mean to imply that the 

 fare which Professor Tyndall offers consists solely of sweetmeats, 

 but simply to warn any who may be inclined to pick out these, and 

 to leave the more substantial food to which they are only intended to 

 impart a flavour, that they must not expect to derive from them any 

 great amount of scientific nourishment. 



The first of the eight lectures contained in this volume treats of 

 the nature of sound, its production, the conditions which determine 

 its greater or less intensity, and the mechanism and velocity of its 

 propagation in air and other media. The effect which the changes 

 of temperature caused by the compression and expansion of air have 

 in increasing the velocity of sound is dwelt upon in this lecture at 

 considerable length, and explained with admirable clearness. 



