REPORT OF THE ACTING SECRETARY. 13 



Under a grant from this fund Mr. A. Lawrence Rotch, director of 

 the Bkie Hill Meteorological Observatory, was enabled to continue the 

 ascensions of hallons- sondes at St. Louis during the different seasons 

 of the year and so to ascertain the annual variation of temperature 

 m the free air at great heights. Twelve balloons were dispatched 

 in July, 1905, and all but two of the attached instruments were 

 recovered. Their automatic records of barometric pressure and air 

 temperature showed an extreme height of nearly 10 miles, with 

 the lowest temperature of 74° F. below zero at a less altitude. The 

 place and time of the descent indicated the average direction and 

 speed of the air currents. All of the last 21 balloons and instru- 

 ments, sent up in April and May, 1906, were returned, some of them 

 having risen 10 miles and encountered a temperature of 85° F. below 

 zero 8 miles above the earth. At about 7 miles a relatively warm 

 stratum was entered, which was found to be at a higher level in the 

 summer and autumn. 



In April, 1906, a Hodgkins grant was requested by Mr. S. P. Fer- 

 gusson, assistant at the Blue Hill Meteorological Observatory, for a 

 study of the differences between the meteorological conditions on the 

 summits of mountains and at the same height in free air. An inves- 

 tigation of this nature being important in its bearings on dynamic 

 meteorology, a small grant to aid in the purchase of the necessary 

 apparatus was approved. 



The apparatus adapted and arranged by Mr. Alexander Larsen 

 for experiments in photographing the spectrum of lightning has been 

 materially improved during the year and the results carefully re- 

 ported. Several interesting photographs have been received from 

 Mr. Larsen, although the conditions have been generally unfavorable 

 throughout the season for securing such, as the electrical storms, 

 which would have furnished them, have taken place in the daytime. 

 The research will continue to be prosecuted as occasion offers. A 

 paper by Mr. Larsen on photographing lightning flashes by a moving 

 camera is included in the general appendix of the Smithsonian 

 Report for 1905. 



In May, 1906, a Hodgkins grant was approved on behalf of Prof. 

 E. L. Nichols, of Cornell University, for an investigation on the 

 properties of matter at the temperature of liquid air. The impor- 

 tance to the physicist and chemist of this field of research, which 

 greatly extends the range of temperatures throughout which investi- 

 gations on the properties of matter can be conducted, is recognized, 

 and the Institution expects that the experiments to be prosecuted 

 under the supervision of Professor Nichols will mark a definite ad- 

 vance in scientific knowledge in this direction. The outline of Avork 

 already submitted notes progress in several interesting researches. 



