SCIENCE. 



[N. S. Vol. II. No. 52. 



the gjas, or rifts in the great lava beds, one 

 to three meters wide and of unknown 

 depth, fairly straight over large areas and 

 explained by the traveller as the result of 

 laccolitic accumulations beneath, by which 

 the surface flows are somewhat raised, 

 arched and cracked. The more fertile dis- 

 tricts are covered with alluvial detritus 

 brought down by streams from the various 

 JokuUs ; but in some cases the wash of 

 gravel and boulders carried by floods from 

 snow melted rapidly by volcanic heat has 

 been so tumultuous as to devastate the sur- 

 face over which it is spread. The rivers 

 here subdivide into numerous distributaries, 

 across which the traveller has to wade re- 

 peatedly. One of the greatest of these 

 stony deserts is the Myrdals-sandr, caused 

 by the eruption of the Kotlugja ; the tre- 

 mendous force of the inundation is shown 

 by the large boulders which have been 

 transported dozens of kilometers from the 

 foot of the highlands down a slope of, 

 for the most part, very small inclination. 

 The Skapter eruption of 1783, "the greatest 

 outflow of lava known to have occurred in 

 historic times," filled the valley of the Eld- 

 vatn and thereby displaced a river which 

 now flows on the lava surface ; but so 

 nearly level is this surface that the river is 

 subdivided into many channels — sixteen) 

 where the author traversed it — no one chan- 

 nel having yet grown to be the master of 

 the whole. Thingvalla Lake appears to 

 have had a cui-ious origin ; a prehistoric 

 lava flood filled a valley, rising to a consid- 

 erable depth above some barrier, and freez- 

 ing a surface layer 32 metres thick ; then a 

 vent was opened by which the still molten 

 under lava was di-ained away, and the sur- 

 face layer settled down in a basin-like de- 

 pression, some 8 km. wide by 35 km. long, 

 in the bottom of which the lake now stands 

 among the disjointed fragments of the lava 

 crust. Wind action is very noticeable ; 

 much of the older rock surface about Cape 



Reykjanes is rounded and polished by the 

 sand blast ; sand dunes are numerous on 

 this peninsula, where ' the most dreadful 

 dust storms ' occur. Much of the pasture 

 soil is wind-blown, collected at first among 

 Uchens and gradiially coming to support a 

 growth of turf; where the grass happens to 

 be worn away, the wind blows away the 

 soil ; thus a farm may be made or marred 

 in a few years. The careful farmer keeps 

 his turf in good repair. 



SABLE ISLAND. 



This lonesome and dangerous island off 

 the coast of N"ova Scotia is recently de- 

 scribed by G-. Patterson (Trans. Roy. Soc. 

 Canada, xii, 1894, 2°, 3-48). A bank that 

 measures about 200 by 90 miles culminates 

 in the island, now twenty miles long and 

 one mile wide. It consists of two parallel 

 ridges of loose gray sand, stretching east 

 and west, and somewhat convex to the 

 south. Between the ridges lies a long nar- 

 row ' lake ' that is sometimes connected with' 

 the sea by inlets on the south, but these are 

 often closed by storms, and then there are no 

 harbors even for small vessels, and landing 

 is generally difficult. Shoals extend far be- 

 yond the ends of the island, east and west, 

 producing a terrible line of breakers with a 

 total length of fifty miles. Strong, con- 

 flicting and irregular currents run about 

 the island; floating wreckage sometimes 

 makes a circuit around it. Fogs and storms 

 ai-e fi'equent; 190 wrecks have been recorded 

 since 1801. The island is raj)idly wasting 

 under the attack of the waves, having been 

 40 miles long by two and a-half wide in 

 1700. About 1814 the rate of wear was 

 nearly a mile a year. In 1881-82 much 

 ground was lost at the western point dur- 

 ing violent storms. In one severe gale, a 

 strip seventy feet wide and a quarter mile 

 long was removed; in another, a strip of 

 the same length and forty-eight feet wide; 

 at one time thirty feet of the land margin 



