146 



NATURE 



[Dec. 23, 1875 



rics,* Mr. Garrod has shown that the pulse-wave augments 

 its rapidity as it gets further from the heart, a result which 

 is specially interesting in connection with those of M. 

 Marey on the undulations in closed tubes, the blood 

 system being similar in all respects. 

 With reference to the changes of the height of the undu- 



augmentation in its rapidity. This depends on the elas- 

 ticity of the tube, which tends to distribute the pressure in 

 the different parts of the liquid column. 



It will be seen from Fig. 2 that the primary direct 

 wave is followed by a more or less numerous series of 

 secondary diminishing minor waves. They are dependent 

 on the rapidity with which the liquid 

 is forced into the elastic tube. The 

 reflected wave may also give rise to 

 secondary undulations. The whole 

 of the foregoing results are repre- 

 sented in a most vivid manner by 

 the translation of their results stereo- 

 scopically or into a figure of three 

 dimensions, represented in Fig. 3. 

 We have never before seen results 

 of a similar kind similarly depicted. 



Among the other results arrived at 

 by the employment of the same in- 

 strument, M. Marey has shown that 

 negative waves, that is of absorption, 

 obey exactly the same laws as do 

 positive waves, or those of compres- 

 sion ; also, in tubes opened at their 

 distant end, if the aperture is large, 

 no reflected wave is produced, at the 

 same time that the intensity of the 

 undulation diminishes from one to 

 the other end, and its rapidity also 

 gradually. 



{To be continued.) 



T 



Fig. 3. 



lation in different parts of its course, it can be proved that 

 the wave has its maxima of intensity at its two ends, its mi- 

 nima in the intermediate part of its course. The wave also 

 changes in form during its progress, this change consist- 

 ing essentially in a diminution in its amplitude and an 



* "Proc. Royal Soc," 1875, p. 130. 



THE ARCTIC WORLD 

 The Arctic World: its Plants, Ani- 

 mals, and Natural Phenomena. 

 (London and Edinburgh : Nelson 

 and Sons, 1876.) 

 HE^Messrs. Nelson have in the 

 present work made a praise- 

 worthy attempt at innovation on the 

 usual style of drawing-room book ; 

 for that " The Arctic Worid " is 

 meant mainly for the drawing-room 

 table its whole appearance indicates. 

 The work is something more than 

 a mere picture-book, though its pic- 

 tures are certainly a striking attrac- 

 tion. The compiler of the text has 

 made an honest, and, we believe, 

 remarkably successful, attempt to 

 carry out the promise of the title- 

 page, and present a satisfactory ac- 

 count of the physical phenomena, the 

 plants, animals, people, and scenery 

 of the entire round of the Arctic 

 regions. There is really a great 

 amount of solid and accurate and. 

 valuable information conveyed, information in itself calJ 

 culated to interest in a high degree any healthy mind, an< 

 which the compiler has had skill enough to put int^ 

 shape without detracting from its interest. 



While we congratulate the publishers on their success- 

 ful attempt to elevate the quahty of drawing-room litera- 



