1870.] Notices of Scientific Works. 75 



Of the construction of roofs many examples are given, and the 

 strains on the parts of different forms are carefully worked out in 

 spans varying from 15 to 240 feet. The methods of determining 

 the strains for differently formed roofs are exceedingly well adapted 

 for obtaining perfect security, and the clear and distinct manner 

 in which the subject is treated must be highly edifying to the 

 student and practical engineer. 



We might enlarge on this, but it could not be expected that a 

 subject of such importance as Iron Koofs and Bridges could be suc- 

 cessfully treated within the limits of a few lectures. There is, 

 however, sufficient matter contained in the work before us to recom- 

 mend its perusal to the consideration of the practical architect and 

 engineer; and looking at the clear and graphic style in which it 

 is written, we feel indebted to the author for this addition to our 

 knowledge of practical science: 



Habit and Intelligence, in their connection with the Laws of Matter 

 and Force : a Series of Scientific Essays. By Joseph John 

 Murphy. 2 vols. London : Macmillan & Co., 1869. 



The intricate problems of the genesis of animal and vegetable life, 

 and of the connection between the human mind and its material 

 abode, will ever be among those which engage and fascinate our 

 intellects of the highest order. The doctrine of a gradual evolution 

 of life, as opposed to that of distinct specific creations, with which 

 the great name of Darwin is associated, and which has been elabo- 

 rated by Spencer, Wallace, and Hooker, has of late years received 

 an extraordinary impulse ; while the parallel theory of a " physical 

 basis of life " has obtained the sanction of some of the highest 

 names in natural science. While these theories are doubtless 

 founded on a substratum of truth unknown to our older naturalists, 

 they are probably mixed up with a considerable amount of error 

 and over-statement, which further investigations will remove. We 

 therefore cordially welcome a work in which the problems of organic 

 life are treated with so free and independent a hand, and with such 

 close reasoning applied to a wide knowledge of facts, as we find in 

 the volumes before us. While adopting the view of the evolution 

 of all living organisms by descent, with modifications, from a few, if 

 not from a single germ, Mr. Murphy holds that the Darwinian 

 theory of Natural Selection from spontaneous variations is inadequate 

 to account for the major part of these modifications, and altogether 

 rejects the Huxleyan principle that the phenomena of life can be 

 accounted for and explained on purely physical principles. 



The first volume of this series of Essays is occupied with 



