A satisfactory rotating bearing (with an insufficient reducing 

 gear) is offered by Winfield H, Smith, Buffalo, N. Y., and the 

 table top may be attached to this, which itself may be attached 

 to a greenhouse bench or other suitable support. The same firm 

 offers an excellent reducing gear (which is needed besides the 

 one coming with the bearing, and which is of course needed with 

 any table built on a bicycle wheel) . A finer type of gear was 

 recently supplied by the Eberbach Company, Ann Arbor, Mich. 

 The electric motor for this work should be of a rating of about 

 14 horse-power. It is to be remembered that the motor and 

 table operate continuously, night and day, for many weeks or 

 even months at a time, and proper lubrication is of course 

 essential. 



Records of Aerial Conditions. 



The non-solution conditions will not be controlled in these 

 tests; the complex of these will vary from hour to hour and 

 from day to day for any series, and it will differ from season to 

 season at the same station and from station to station at the 

 same season. In order to secure a rough description of this com- 

 plex for each experiment, four kinds of records are to be ob- 

 tained. These have to do with (1) air temperature, (2) reading 

 of white spherical porous-cup atmometer, (3) reading of black 

 spherical porous-cup atmometer, and (4) duration of sunshine. 

 Methods for these records are set forth below. 



(1) The records are to show the maximum and minimum 

 air temperature in shade at the experiment location for every day 

 of each experiment. These records may be obtained by the use 

 of a max.-min. thermometer (read daily after the occurrence of 

 the maximum for the day) , or they may be taken off from a ther- 

 mograph record sheet. The data are to appear in terms of the 

 centigrade scale. 



(2), (3) Standardized black and white spherical atmometer 

 cups, with simple mountings, will be furnished by the committee 

 at cost ($10.00 for two whites and two blacks, with two simple 

 mountings) . Orders should be sent to Baltimore. The two in- 

 struments should stand on the rotating table, within the circular 

 area left free by the peripheral row, or rows, of cultures. They 

 should be operated with distilled water, the porous surfaces 

 should be scrubbed with distilled water and a tboth-brush once 

 a week, and they should be read weekly, always at the same hour 

 of the day. Since water is apt to enter the instrument during the 

 operation of scrubbing, this operation should take place after 



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