412 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



particularly recommended by M. Senequier for hatching out 

 the eggs of exotic birds. He received the parents of the 

 stock from one of his friends, who was ignorant whence they 

 were originally derived. It may have been developed in 

 that locality under the influence of long-continued topograph- 

 ical conditions. Specimens of these were to be brought for- 

 ward at the exhibitions of the society in 1873. 10 B^ Decern- 

 her 1872, 878. 



PROPER TEMPERATURE OF SILK-WORM HOUSES. 



According to Dr. Collet, a heat of 86 Fahr. is absolutely 

 necessary for the establishments in which the silk-worms are 

 being reared; and to obtain this he proposes to introduce 

 stove heat in these magnaneries, so as to have the tempera- 

 ture of 86 Fahr. up to the first moult, and 95 between this 

 moult and the fifth. The advantages of this system of heat- 

 ing to a high temperature are that the rearing is accomplished 

 in twenty days instead of forty, involving, in such accelera- 

 tion, a much greater immunity from disease among the worms, 

 and, as the windows can be kept closed, they are protected 

 against sudden variations of temperature. The leaves fed to 

 the silk-worms, too, are entirely eaten up, nothing being left 

 but the nerves and the peduncles, instead of their being a 

 considerable amount of waste, as under other circumstances. 

 3 J5, May 8,1873, 60. * 



EXTERMINATION OF FIELD-MICE. 



The question of the best method of exterminating field- 

 mice is one that occupies the attention of the German agri- 

 culturists to a much ofreater extent than in our icountrv-, 

 where it is only exceptionally that the numbers of these 

 pests become so gjeat as to cause A^ery serious mischief 

 Their ravages in America appear, in a considerable degree, 

 to be confined to the destruction of young trees in nurseries 

 during the winter season ; but in Germany the loss of crops, 

 annually, is said to represent a very considerable percentage. 

 So grave, indeed, is the importance of the question, that it in- 

 vokes, from time to time, the direct action of the government 

 of the several states, which pay out large sums every year, 

 although the price per capita for the destruction of the mice 

 is fixed at a very low rate. They also give rewards for the 



