I 



THE GEMS OF THE NATIONAL MUSEUM. 823 



A fact remarked by Humboldt as accompanying tbe earthquake of 

 the 4th of November, 1799, at Curaana, was also observed at Guate- 

 mala on the 8th of December, 1859. I refer to a sudden and consid- 

 erable deviation of the magnetic needle, which still continues. To 

 account for it, I propose the theory of a change by the shock in the 

 disposition of the neighboring strata. 



A series of more than seven hundred shocks between the 20th and 

 31st of December, 1879, two of which were disastrous, and which 

 caused much alarm at San Salvador, was the prelude to the appear- 

 ance, in the neighboring Lake of Ilopango, of a new but ephemeral 

 volcano, whose mass caused the lake to overflow its banks and to pro- 

 duce a terrible inundation in the valley of the Rio Jiboa. The event 

 has been made the subject of a detailed and very interesting study by 

 Messrs, Goodyear and Rockstroh. I will only observe respecting it 

 that two hundred and thirty-seven explosions took place on the 4th of 

 March, 1880, between twenty-five minutes past nine and twenty min- 

 utes past ten in the morning, and eight hundred and ninety-seven ex- 

 plosions between eighteen minutes past seven in the evening of the 

 following day and seventeen minutes past three on the next morning. 



The retumbos heard at San Salvador and in Colombia on the 27th 

 of August, 1883, were doubtless the echo of the eruption of Krakatoa. 

 I am satisfied that if such a work as I have performed for the small 

 fraction of Central America were done for the whole system of the 

 Cordilleras, from Cape Horn to Behring Strait, and if the different 

 governments would establish meteorologico-seismic observatories, like 

 the one I have directed for four years at San Salvador, it would be 

 possible, in this home of volcanic activity, to form some sound theory 

 of these interesting and terrible phenomena, and perhaps to find some 

 means of announcing them beforehand, as we predict storms on the 

 Atlantic. — Translated for the Popular Science Monthly from the Re- 

 vue Scientifique. 



THE GEMS OF THE NATIONAL MUSEUM. 



By GEORGE F. KUNZ. 



THE collection of gems exhibited by the National Museum at the 

 Cincinnati and New Orleans Expositions is now on exhibition at 

 the rooms of the Museum in Washington. This much-needed accession, 

 representing a small part of the appropriation for the World's Fair, 

 promises to be one of the most attractive and instructive features of 

 the museum. The large number of visitors who examined the collec- 

 tion, both at the fairs and in its present location, can testify to its inter- 

 esting character. Although a mere beginning, it is the most complete 

 public collection of gems in the L'nited States. It is contained in two 



