GEOLOGY. 225 



a volcanic vent in the midst of a lake, about which a large island imme- 

 diately proceeded to build itself. The lake is called the Ilopango See, 

 and is nine kilometers long and seven kilometers wide. The level of its 

 waters was raised before the eruption to such a degree as to make a 

 flood in the valley of its outlet; and its waters were so heated and im- 

 pregnated with sulphureted hydrogen as to exterminate the fish, which 

 were very abundant in the lake. The dead fish were buried with great 

 labor and expense, in order to avoid pestilence. Tlie volcanic cone in the 

 lake repeatedly grew to considerable dimensions, and was as repeatedly 

 blown to pieces. This lake is surrounded by volcanic cones, and re- 

 minds one of the well-known Laacher See, which, however, has no out- 

 let. One looks forward to the time when volcanic phenomena near us 

 will receive the critical and continuous study which alone can make 

 them of extreme interest. 



Some other European volcanoes beside Vesuvius and Etna have been 

 monographed. The work of F. Fouqu6, aided by the French Govern- 

 ment, on Santorin and its erui^tions, is one of the most beautiful and 

 complete treatises which has been devoted to a volcano. The topog- 

 raphy of the island, the history of all the eruptions, records of which 

 exist in history, outlines illustrating the various changes that have 

 taken place in the form and extent of the island, and beautiful pictnres 

 of the microscopic sections, illustrating the mineral composition of the 

 various eruptions, all combine to make an interesting and instructive 

 volume. Santorin is a crescent-shaped island in the Grecian Archipel- 

 ago. It has several craters, part of which are submarine. The last 

 eruption occurred in January, 18GG, which materially increased the 

 size of the island. This, together with the other historic and the pre- 

 historic eruptions, are treated in much detail; and the 440 pages of this 

 quarto volume show how greatly science is enriched by careful study of 

 snuill areas. 



LOESS. 



The question of the origin of the loess formations has excited much 

 interest. Loess is that very fine-grained calcareous unstratified deposit 

 which occupies the river valleys of many rivers, notably the Rhine. It 

 is characterized by the inclusion of the shells of land snails, and by 

 concretions of limestone, which take very peculiar shape, looking very 

 much like potatoes, but liable to take any form. The Germans call them 

 loess dolls. This deposit is so firm in its texture that when a cut is 

 made through it, its walls will not crumble and wash away, as do the 

 walls of ordinary loose material, but for years they will maintain their 

 vertical surfaces, and preserve marks that are made in them with knives 

 or walking sticks. Indeed, names and i^ictures carved an these loess walls 

 form one of the characteristic fossils of the formation. Von Richthofen, 

 who knew this formation well, has shown that it, or a like formation, exists 

 over large areas in the Asiatic interior, and he has considered that it is 

 S. Mis. 31 15 



