28 REPORT OF THE SECRETARY. 



we were informed by him that he had been robbed in Mexico, and that 

 the instruments had been captured and destroyed. Not having re- 

 ceived a final report from Baron Yon Miiller, to render the observa- 

 tions which had been obtained from Mexico available to science, they 

 were placed in the hands of Mr. Sonntag on his return to Washington, 

 and have been reduced by him at the expense of the Institution. He 

 has also appended a series of notes relative to the volcano of Popo- 

 catepetl and its vicinity, and also a series of barometrical and trigo- 

 nometrical measurements of heights of various places in the vicinity 

 of the city of Mexico. The observations included those for the 

 declination or variation, the inclination or dip, and, lastly, those for 

 the relative intensity of the magnetic force. A series of observations 

 for each of these elements was made at the following places, namely, 

 Vera Cruz, Potrero, Cocolapam, San Andres, Mirador, city of Mexico, 

 Chalco, and Tlamacas. The average variation of the needle from the 

 whole series of observations was about 8^° east; at the city of Mexico 

 it was 8° 46' east. The average dip for the whole region was about 

 42i°, and for the city of Mexico 41° 26'. 



The interesting fact is noted in the appendix that the southwestern 

 wall of all the recent Mexican craters observed by the author is higher 

 than the northeastern wall — a phenomenon probably due to the action 

 of the trade-winds constantly impelling the ashes and cinders from 

 the northeast to the southwest. The elevation of eleven different 

 places was determined, including the city of Mexico and the highest 

 peak of Popocatepetl. The former was 7,472.8 feet, and the latter 

 17,817.6 feet. 



We regret very much the loss of the magnetic instruments, not 

 only on account of the use which might be made of them in deter- 

 mining the magnetic elements of different portions of the American 

 continent, but also on account of the interest which attaches to them 

 from having been employed in the observations by Dr. Kane. 

 They have, however, done good service; and although the result of 

 the co-operation of Baron Yon Miiller has not been as fortunate as we 

 could have wished, still it has added something of considerable value 

 to our knowledge of the terrestrial magnetism of this continent. 



Another memoir, which will form a part of the 11th volume of 

 "Contributions," is on the American storm of December 20, 1836, 

 and the European storm of December 25 of the same year, by Pro- 

 fessor Elias Loomis, of the University of New York. 



