856 



SCIENCE. 



[N. S. Vol. XV. No. 387. 



There are thus two opposing forces act- 

 ing on the anemometer, the one due to the 

 motion of the ions and the other due to the 

 transfer of heat from the centers outward. 

 The direction of rotation depends upon 

 which of these forces is in excess. No at> 

 tempt has yet been made at quantitative 

 measurements, although such measure- 

 ments could probably be made by a tor- 

 sional suspension of the anemometer in a 

 vessel as large as that described in experi, 

 ment 10. 



It is my hope in the near future to in- 

 vestigate a possible diiferenee of potential 

 between the walls and the center of the ves- 

 sel, and also to study the motion of the 

 cathode rays in a Tesla field. 



In addition to furnishing direct support 

 to the Maxwell equation, the experiments 

 may be of some value from their bearing on 

 the electron theory of electricity. The 

 electrodeless discharge consists of a rapidly 

 alternating current of electricity similar to 

 that which would be produced in a metal 

 ring placed within the coil. It thus ap- 

 pears that such current is at least accom- 

 panied by ionic motion even if such motion 

 does not constitute the current itself. 



Bergen Davis. 



GoTTlNGEN, February 17, 1902. 



TEE TROPICAL LABORATORY AT MIAMI, 

 FLORIDA* 



The extent to which the government of 

 the United States is making provision for 

 scientific investigation in connection with 

 the work of its various departments, not- 

 ably that of the Bureau of Plant Industry, 

 is a matter of congratulation. To scientific 

 workers especially, it is a gratifying fact 

 that the laboratories established primarily 

 for the study of plant diseases and other 

 subjects of a practical nature are being 

 thrown open to investigators of widely dif- 



* Read before the Michigan Academy of Science, 

 March 27, 1902. 



ferent aims, their facilities being freely 

 placed at the disposal of students engaged 

 in any line of research whatever. One of 

 these, the Tropical Laboratory of the 

 United States Department of Agriculture, 

 has been established so recently and offers 

 such exceptional advantages that its loca- 

 tion and facilities should be widely known. 

 This laboratory, located at Miami, Pla., in 

 1899, was formally established under its 

 present name in 1902. After the discourag- 

 ing failure of much of the experimental 

 work at Eustis, Fla., occasioned by the dis- 

 astrous freezes of 1894-95, it became 

 apparent that another place must be 

 selected less subject to climatic vicissitudes, 

 and thus far there is every reason to believe 

 that the location now chosen will admirably 

 fulfil the requirements for such a station. 



Miami is situated a little south of the 

 twenty-sixth parallel of latitude, in direct 

 communication with the north by rail, and 

 with Nassau, Havana, and Key West by the 

 Peninsular and Occidental Steamship Line. 

 The city, only a few miles from the Ever- 

 glades, is healthfully built on the coral 

 breccia which forms the underlying rock, 

 and looks out on Biscayne Bay, landlocked 

 by the northeastern extension of the 

 Florida Keys. Its delightful climate, per- 

 mitting all sorts of outdoor study and ex- 

 ploration in midwinter, is not the least of 

 its many advantages. The laboratory, 

 situated a mile south of town, is easily 

 reached in ten minutes by wheel over a 

 smooth rock road. Six acres of land belong 

 to the station, upon which experiments in 

 acclimatization and plant breeding are in 

 progress. The laboratory building is a 

 plain but substantial and well -arranged 

 structure, with office and library in which 

 are shelved upwards of two thousand vol- 

 umes, including pamphlets and periodicals, 

 among which are the Botanisches Central- 

 Matt, Botanischer Jahresbericht, Science, 

 the Botanical Gazette and other current 



