26 REPORT OF THE SECRETARY. 



The sixth set of tables is for tlio conversion of the corresponding 

 surface or square measures of the preceding table into each other. 



These measures, which are also founded on the late terrestrial ele- 

 ments of Bessel, have been selected with reference to the frequency 

 of use in the consultations of the official publications of different 

 European nations. Each of the above tables furnishes the value of 

 every full number from 1 to 100, in six figures for the measures of 

 length, and seven for those of surface. 



The seventh set of tables gives the velocity of rotation of the earth 

 for each degree of latitude, expressed in the measures of length most 

 frequently used, and will facilitate computations in regard to the 

 velocity of the wind. 



The whole series comprises over 17,000 separate numbers, filling 

 70 large octavo pages. 



It is proposed to add to these tables one giving the length of time 

 of sunshine in different latitudes for each day in the year, and, to 

 complete the series, a number of tables for calculating the resultant 

 direction of the winds. 



It is believed that these tables will be received as a welcome addi- 

 tion to the physical tables previously published by the Institution, 

 and which are now well known and used in every partof the civilized 

 world. They will be of value to .the meteorologist and physical 

 geographer, as well as to the statistician and political economist. 

 The first set is indispensable for easily computing distances on globes, 

 maps, &c. ; the second will greatly facilitate the use of the numerous 

 data furnished by travellers, scientific publications, and especially 

 the official statistical information contained in the various documents 

 of the states of Europe. The selection of the various measures is 

 made with special reference to the latter — as the myriametre and 

 kilometre for the study of later French publications, and the com- 

 mon French league for the older ones ; the Austrian and Prussian 

 miles, the Russian werst, and English statute mile for publications in 

 the countries where those measures are used. In the preparation of 

 these tables a question has arisen whether an additional series 

 should be constructed for the conversion of the American foot into 



the English, between which there is, unfortunately, a slight dif- 

 ference. 



Reports. — The . annual reports to Congress are printed at the ex- 

 pense of the government, with the exception of the cost of the 



