December 15, 1904]' 



NATURE 



147 



the movement, that Duchenne comes much nearer the 

 truth than the brothers Weber, muscular action playing 

 a much larger part than the force of gravity. Those 

 who have watched the passive movements of a para- 

 lysed leg during attempts at progression will have no 

 difficulty in accepting Prof. Fischer's results. 



The problem of estimating theoretically the force 

 necessary to produce the forward swing of the lower 

 cxtremitv in walking is an extremely complicated one. 

 Prof. Fischer regards the lower extremity as a pen- 

 dulum made up of three segments, each of which 

 undergoes certain secondary movements during the 

 swing of the entire extremity. Further, the hip joint, 

 from which the pendulum is suspended, undergoes an 

 irregular forward movement during the swing of the 

 limb. The resistance and elasticity of the muscles and 

 ligaments and the friction at the various joints are 

 factors which can only be approximately estimated. 



By means of photographic records Prof. Fischer was 

 able to subdivide the forward swing into forty and 

 forty-one equal phases of time, and by estimating the 

 amount of force in action during each phase he shows 

 that gravity alone can account for only a minor frac- 

 tion of the force necessarily expended in the movement. 

 Further, the positions assumed by the foot, leg, and 

 thiefh during a forward swing show distinctly that 

 various groups of muscles are then in action. He 

 recognises four periods in the forward movement of 

 the limb, each of which is characterised by the action 

 of a distinct group of muscles. In the commencing 

 phase the ilio-psoas bends the thigh on the body, the 

 rectus femoris extends the leg forwards, the tibialis 

 anticus bends the foot upwards; in the second phase 

 the gluteus maximus and hamstring muscles draw 

 the thigh backwards ; in the third phase the knee is 

 flexed by the gastrocnemius and short head of the 

 biceps ; in the final phase the muscles in front of the 

 leg are again in action, and remain powerfully con- 

 tracted until the sole of the foot is again planted on 

 the ground. 



These results are certainly much more in keeping 

 with clinical and everyday experience than those of the 

 brothers Weber. Many who only occasionally take 

 long walks must have observed that one of the first 

 groups of muscles to give out are those in front of the 

 leg, and that they feel painful only at the end of the 

 forward swing, when the heel reaches the ground — 

 the period at which Prof. Fischer shows these muscles 

 come most powerfully into action. A. Keith. 



earthovakes. 



Earthquakes. By Clarence Edward Dutton, Major, 

 U.S.A. Pp. xxxiii + 314; 63 illustrations. (London: 

 John Murray.) Price 6s. net. 



EPITOMISED and carefully digested accounts of 

 seismological investigations made during the last 

 twenty-five years are few in number. Two have been 

 published in England, a compilation has been " made 

 in Germany," and now we have a volume from the 

 distinguished geologist, Major C. E. Dutton, of the 

 United States. All told, therefore, we have only four 

 books which give the uninitiated some idea of what 



NO. i«33, VOL. 71] 



the new seismology means and what it has accom- 

 plished. About the old seismology, volumes, papers, 

 and particularly sermons exist in thousands. But if 

 we except a few, and amongst the few the works of 

 Mallet stand high above the rest, all they give are 

 reiterated narratives of what people saw and heard, 

 now and then enlivened by some wild hypothesis or 

 pious reflection. 



Major Dutton 's work belongs to another category, 

 and rather than telling us what earthquakes do, his 

 main object has been to tell us what they are, and 

 while doing this he has kept abreast with the work 

 of others which his own inquiries in the domain of 

 seismic and volcanic activities have enabled him to 

 present in a terse and accurate form. 



Everything is discussed with a minimum of mathe- 

 matics from a strictly scientific standpoint, whilst that 

 which is sensational has properly been most carefully 

 put under taboo. A justification for the exclusion of 

 what is of practical importance, which gives not only 

 to the man in the street but to Governments some 

 inkling as to the use of earthquakes, is not so apparent. 

 It is extremely likely that a Prime Minister may not 

 care a twopenny-bit whether the inside of the world 

 on which he lives is red hot or stone cold, while he 

 might be extremely interested to know that seismo- 

 grams may afford a satisfactory explanation for the 

 interruption of his cablegrams. The importance of 

 earthquake writings to communities who have been 

 alarmed by accounts of disasters in foreign countries 

 is self-evident, while it would at least be consoling to 

 those w ho were suddenly cut off from the outer world 

 by the failure of their cables to learn whether such 

 failures were the result of an operation of war or of 

 nature. A knowledge of how to construct so that 

 earthquake effects should be minimised means the 

 saving of life and property in countries subject to 

 seismic disturbances. Seismic charts indicate posi- 

 tions where it is dangerous to lay deep-sea cables, 

 whilst they tell the hydrographer where he may expect 

 to find changing depths. In these and in a variety of 

 other directions seismology helps to make communities 

 comfortable, and at the same time acts as incentive 

 to create a popular interest in and to obtain support 

 for a young science. But as Major Dutton defines his 

 standpoint, and as a volume of 300 pages cannot con- 

 tain everything, our remarks on omissions must only 

 be taken as indications of the hydra-headed nature of 

 seismology. 



The first four chapters are chiefly devoted to the 

 cause of an earthquake, which is defined as anything 

 that " calls suddenly into action the elasticity of the 

 earth." Explosions at volcanic foci produce a local 

 trembling, but they are comparatively of rare occur- 

 rence and seldom disturb large areas. When a long 

 fault line is produced, and a large territory carrying 

 perhaps mountain ranges drops down along its length, 

 instrumental observations have revealed the fact that 

 the world may be shaken as a whole. Subsequent 

 adjustments along such a line due to intermittent re- 

 covery from overstrain and settlements of disjointed 

 materials give rise to numerous after-shocks which 

 are onlv sensible over areas of small size, and it seems 



