REPORT OF TEE SECRETARY. 35' 



Researches. — Mr. L. W. Meecli has continued his mathematical re-' 

 searches in regard to the light and heat of the sun, and, since the 

 date of the last Report, has succeeded in integrating some of the an- 

 alytical expressions which had previously appeared likely to prove 

 exceedingly troublesome, and the analysis is now sufficiently advanced 

 for another publication. His next memoir will treat of the relative 

 intensity of the sun's rays after passing through the air to the earth's 

 surface. It will be recollected that his former memoir presented, in 

 tables and curves, the intensity of the sun' s rays at the exterior of 

 the atmosphere. The primary formula, to be given in this memoir, 

 has been demonstrated and verified, and the derived formulas are 

 mostly made out for the range and other phases of the intensity of 

 the light and heat. These depend on what are called elliptical func- 1 

 tions, and are much more complicated than those of the former paper. 

 Before curves can be drawn from them, the numerical values for every 

 five degrees of latitude are to be computed and checked, which will 

 require the labor of several months. To defray the expense of this,, 

 another small appropriation will be required. The success of the 

 previous labors of Mr. Meech warrants this expenditure, from funds 

 intended for the increase of knowledge, since the results which can 

 now be obtained from his formula will, in all probability, be consid- 

 ered standard elements in the physical theory of heat. 



Dr. Wolcott Gibbs has continued his chemical researches, and a paper 

 in relation to them /will probably appear in the next volume of Con- 

 tributions. It will present new processes for the separation of all the 

 platinum metals in a state of absolute purity. These are very simple, 

 and easy of execution, and not only apply to the separation, but to 

 the quantitative analysis of mixtures of the different metals of this 

 group in almost any proportion. The researches also involve the 

 preparation and properties of a new and remarkable series of salts, 

 which, it is thought, will remove the difficulties with which the sub- 

 ject has hitherto been surrounded. 



It was stated in the last Report that one of the most important op- 

 erations in which the Institution had been engaged during the previ- 

 ous year was the construction of a map to present at one view the 

 arable, forest, and sterile portions of the United States. The design 

 at first was merely to exhibit the limits or boundaries of these por- 

 tions of the country, and this has been faithfully executed by Dr. J. 

 G. Cooper, to whom the work was intrusted, as far as the materials 



