238 NATURAL HISTORY OF AQUATIC INSECTS CH. 



equal parts. The degrees were marked so that each 

 corresponded to an increase of voluiTiC equal to one 

 of the thousand parts. It happened that the alcohol 

 (not pure alcohol) which he used to fill the thermo- 

 meter dilated ^^fu of its volume during the rise of 

 temperature from the freezing to the boiling point of 

 water, and Reaumur was thus led to divide the cor- 

 responding part of the tube into eighty degrees. 

 Hence the scale which was long used, almost to the 

 exclusion of others, in continental countries. ''; 



Among the many physical inquiries pursued by ? 

 Reaumur are those which relate to the evaporation 

 of snow and ice during frost, and to the action of 

 freezing mixtures. 



Natural History was a favourite study with 

 Reaumur throughout his life, and gradually took 

 almost entire possession of his time and energies. 

 Among his early researches are a description of the 

 organs of locomotion in Star-fishes, and experiments 

 to prove that the Cray-fish and Lobster have the 

 power of reproducing lost limbs. In 1734 began the 

 publication of his magnificent History of Insects, 

 which though incomplete, fills six quarto volumes 

 abundantly furnished with plates. The life-histories 

 of many Lepidoptera, Caddis-flies and Aphides, of 

 the larvjE which prey on Aphides, of the Cicada, of | 

 gall-making Insects, of various Diptera, of the Saw- 

 flies, of Bees and their economy, of Wasps, Ichneu- ll 

 mons. Ant-lions, Ephemera.% Dragon-flies, and lastly of 

 the Horse-tick, Hippobosca, occupy these elaborate and 

 beautiful memoirs. The patient and sagacious observa- >j 

 tions here recorded in language of transparent clearness '-i 



ii 



