FRESHNESS OF TREATMENT 187 



carefully, found to be suitable, seized hold of, and at once, after a few chips and 

 modifications (if necessary) laid into this big pyramid, in the climbing of which the 

 youth of this country will hereafter have free scope for trying their strength, and 

 looking down from the sides and the top of it upon this puzzling intricate physical 

 world.... 



"The world of which they give the natural philosophy is real and not ideal. It 

 is not the abstract world of Cambridge examination papers in which matter is 

 perfectly homogeneous, pulleys perfectly smooth, strings perfectly elastic, fluids 

 perfectly incompressible.... but it is the concrete world of the senses, which approxi- 

 mates to but always falls short alike of the ideal of the mathematical as of the 

 poetic imagination." 



The review finishes with a reference to the doctrine of the dissipation 

 of energy, and a mild expression of wonder as to what the " natural theologian " 

 will make of it. 



To a real student of physical science conversant with the text-books 

 of the middle of last century Thomson and Tail's Treatise on Natural 

 Philosophy must have come as a revelation. Instead of the usual 

 approach through Statics, with Duchayla's proof of the parallelogram of 

 forces, he found himself introduced to what the authors called Preliminary 

 Notions, arranged in four chapters under the titles Kinematics, Dynamical 

 Laws and Principles, Experience, Measures and Instruments. In opening 

 with the subject of Kinematics or the Geometry of Motion, Thomson and 

 Tait followed to some extent the example of certain recent French writers, 

 such as Delaunay and Duhamel ; but, in thus discussing motion and 

 displacement apart from dynamical relations, they carried out the idea 

 much more thoroughly than had ever been done by their predecessors. 

 In other English books of the day there was absolutely nothing like it. 

 In the first few paragraphs the geometrical conceptions of curvature and 

 tortuosity are treated in a novel and elegant manner as illustrative of 

 motion along a curve or line of changing direction. Even the familiar 

 quantities, velocity and acceleration, are discussed in a fresh way ; but it is 

 in the later sections of the first chapter that originality of treatment rivets 

 the attention of the careful reader. Simple Harmonic Motion, which is 

 the foundation of all kinds of wave-motion, is the avenue by which Fourier's 

 Theorem is approached. Composition of angular velocities, the rolling of 

 curves and surfaces on one another, curvature of surfaces, etc., etc., fall 

 into line as the subject develops. An altogether unique part is to be 

 found in 135 to 138 inclusive (somewhat extended in the second edition). 



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