LETTER OF TRANSMITTAL. 
Honolulu, Hawaii, August 15, WIS. 
Sir: I have the honor to submit herewith and recommend for 
publication, as Bulletin 30 of the Hawaii Agricultural Experi- 
ment Station, a paper dealing with the Effect of Heat on Hawaiian 
Soils, by W. P. Kelley, chemist, and William McGeorge, assistant 
chemist of the station. The effect of heat upon Hawaiian soils, 
including highly manganiferous soils, has been found to be decidedly 
beneficial to the growth of all kinds of plants. The careful study 
of the various chemical and mechanical changes produced in soils 
by the application of heat, as set forth in this bulletin, throws con- 
siderable light upon the reasons for this beneficial effect. Studies 
on the effects of heat on soils have usually been confined to a few 
plant-food elements, whereas in this bulletin a large number of the 
inorganic and organic substances are considered. The bulletin is, 
therefore, considered a distinct contribution to the literature of this 
interesting phase of soil work. 
Respectfully, E. V. Wilcox, 
Special Agent in Charge. 
Dr. A. C. True, 
Director Office of Experiment Stations, 
U. S. Department of Agriculture, Washington, D. C. 
Publication recommended. 
A. C. True, Director, 
Publication authorized. 
D. F. Houston, 
Secretary of Agriculture . 
(3) 
