WEATHER BUREAU. 289 



and specify a complete equipment for the protection from lightning 

 of the buildings and structures at the Morgan Hoi-se Farm, Middle- 

 bury, Vt. The work of instiillation was carried out by the farm 

 workmen, and an effective system of protection provided at a small 

 part of the ordinary cost of such work. 



In furtherance of the active cooperation of the Weather Bureau 

 with other departments of the Government, instruments have been 

 installed at Priest River, Idaho, and Cloquet, Minn., for the Forest 

 Service, and equipments have also been sent to the forest experiment 

 stations at Ephraim, Utah, and Quincy, Cal., where they will soon be 

 installed. In cooperation with the Bureau of Mines, instruments have 

 been supplied and provisions made for collecting humidity and tem- 

 perature data over central Illinois, to be used in the study of causes 

 and prevention of mine disasters. 



In connection with the extensive arrangements made during the 

 year to observe and study the conditions attending frosts in orchards, 

 equipments were placed at 39 points of observation at 10 different 

 orchard stations in North Carolina. Less extensive provisions were 

 made for similar observations at Grand Junction, Colo., Provo, Utah, 

 and a few stations in Oregon. Plans in hand for a general extension 

 of studies in other important fruit sections will call for additional 

 equipments. 



Kiosks were purchased for 10 stations, and these are now in full 

 operation, except at three stations where the work of erection is 

 almost completed. 



INSTRUMENTS FOR SPECIAL RESEARCH WORK. 



The development of special apparatus for the measurement of 

 solar radiation was extended during the year and equipments of the 

 Marvin pyrheliometer were completed for use at Washington, Mount 

 Weather, Madison, Lincoln, and Santa Fe, as earlier mentioned. 



It has been known for a number of years that the velocities of the 

 wind, as shown by the standard types of anemometers, are increas- 

 ingly erroneous at velocities of 50 to GO miles per hour and higher. 

 As the exact evaluation of these indications can be determined only 

 by comparatively elaborate investigations, Prof. Marvin was di- 

 rected to take up this important problem. In accordance with his 

 recommendations, two methods of investigation will be conducted. 

 Preparations are already well advanced for making these tests by 

 means of an anemometer whirling machine. This apparatus consists 

 of a horizontal arm 30 feet in length, which revolves about a vertical 

 axis and carries at its outer end the anemometer to be tested. Tests 

 of a satisfactory nature can be obtained by this means at different 

 velocities up to 70 or 80 miles per hour. The second method of test- 

 ing will be carried out in a so-called wind tunnel. A large blower, or 

 fan, will drive the air through a closed channel or duct producing 

 conditions under which the velocity of the anemometers subjected to 

 the current thus created can be measured accurately by well-known 

 dynamic principles, as well as by the aid of special types of pressure 

 gauges. General plans for the equipment required are now in the 

 hands of blower companies, with a view to further development along 

 lines of greatest efliciency and economy of power. With this ap- 

 paratus the velocities will be carried beyond 100 miles per hour. 



70481°— AGB 1912 19 



