XII LIST OF ILLUSTRATIONS. 



PAGE 



Fig. 24. — Showing two successive positions of the arm of the instru- 

 ment, and the corresponding positions of the tracing 



points of the levers 120 



Fig. 98. — Elastic point, tracing on a piece of smoked glass . . 239 

 Fig. 102. — Transmission of a to-and-fro movement by means of a 



simple traction thread 245 



ILLUSTRATIVE APPARATUS. 



Fig. 1. — Showing the transformation of the electricity of a coil 



into mechanical work, heat, light, and chemical action . 10 

 Fig. 6. — Appearance presented by the waves in a muscular fibre . 36 

 Fig. 9. — Transformation of heat into work by a strip of india- 

 rubber 39 



Of the Flight of Insects. 



Fig. 84. — Artificial representation of the movements of the insect's 



wing 199 



Fig. 85. — Changes in the plane of the insect's wing . . . . 200 

 Fig. 87. — Artificial insect, to illustrate its flight .... 202 

 Fig. 88. — Arrangement of the artificial insect, so as to obtain the 



hovering motion or the ascending flight . . . . 205 



Of the Hovering of the Bied. 



Fig. 90. — Instrument to illustrate the hovering of the bird . .217 



Fig. 91. — The same, explaining the upward turn , . , . 218 



Fig. 92. — ,, ,, downward ditto . . . 219 



ANATOMY. 



Fig. 13.— Skeleton of a flamingo (after Alph. Milne-Edwards; the 

 wing is very large, the sternum very short and deep, 

 which indicates the size and the shortness of the pectoral 

 muscles . 72 



Fig. 14.— Skeleton of a penguin: sternum very long, wing very 



short .......... 73 



Fig. 15. — Skeleton of the wing and sternum of the sea swallow 

 (Hirundo marina); showing the extreme shortness of 

 the sternum, and the great length of the wing . . . 74 



Fig. 89.— Diff'erent curves in the wing of the bird at various parts of 



its length . .210 



Fig. 117. — Active and passive parts of the bird's wing . . . . 276 



Fig. 83. — Structure of the insect's wing 196 



