20 



SCIENCE 



[N. S. Vol. XXVIII. No. 705 



there is a lake of molten lava, in the shape of 

 the figure eight, approximatesly 800 feet long by 

 400 feet wide. Near the center of the northern 

 lobe of the lake is an island some 78 feet in 

 length, in the shape of a half moon. Within the 

 little bay formed by the points of this island 

 there is an almost constant boiling of the molten 

 lava, with explosive bursts of gas every minute 

 or so, which throws masses of the molten fluid 

 into the air some 30 to 40 feet, and scatters it 

 over an area of approximately 100 feet in diam- 

 eter. Immediately after each outburst of gas a 

 tremendous suction draws the lava from a radius 

 of 100 feet of the bay into a vortex like that of a 

 maelstrom, great cakes of lava 15 or 20 feet in 

 diameter being turned up on edge, sucked in and 

 disappearing like chips down a whirlpool. 



Immediately north of the island, at a distance 

 of not more than 100 feet therefrom, there is a 

 gigantic outpouring of lava from beneath, without 

 any bubbles or explosions. It looks like an enor- 

 mous spring, the lava simply welling up and flow- 

 ing ofiF in all directions. The current is so rapid 

 that the surface of the lake does not have time to 

 cool, except in spots, and these spots are at fre- 

 quent intervals upheaved by convulsions from 

 beneath, and the black crust engulfed in the 

 liquid lava beneath. The crusts striking the 

 banks of the lake, which are from four to six feet 

 high, are either shoved bodily upon the banks, 

 like ice cakes in the Arctic, or upturned on edge 

 and swallowed up in the fiery depths below. At 

 intervals boiling spots appear at various points 

 on the lake; engulfing the black cakes of lava 

 floating thereon. The outpouring of the lava 

 from the great spring is so great that the level 

 of the liquid lava is raised faster than the sur- 

 rounding banks can retain it, and at frequent 

 intervals the banks give way and torrents of lava 

 flow out into the surrounding territory in the pit, 

 imtil that portion of the pit is raised to a level 

 that stems the flood. 



This action has been going on now for several 

 weeks, the lake constantly enlarging and the floor 

 of the pit being raised by the overflows of lava. 



The brilliancy of action can be judged from the 

 fact that a lantern is not needed in crossing the 

 rough floor of the crater, the light from the lake 

 being more than sufficient to show the trail in 

 its details. The glare of the lake can also be 

 seen any clear night from Hilo and Honuapo, 

 at distances of 31 and 35 miles, respectively. 



The probability is that tbis brilliant dis- 

 play can be seen for several weeks or montlis 



yet; but it would be well for visitors to lose 

 no time in starting for tbe volcano for fear 

 of disappointment. It will be many years 

 before another equally good opportunity is 

 likely to present itself. 



C. H. Hitchcock 

 Hanover, N. H., 

 June 10, 1908 



SCIENTIFIC BOOKS 



Air-ships, Past and Present. By A. Hilde- 

 BRANDT. Translated by W. H. Story. Pp. 

 364; 222 illustrations. New York, D. Van 

 Nostrand & Co. Price, $3.50 net. 

 There have been hitherto few satisfactory 

 books in English upon aerial navigation and 

 information in newspapers has not always 

 proved accurate. We now have, however, a 

 book by a thorough expert, Captain Hilde- 

 brandt, instructor in the Prussian Balloon 

 Corps, who wrote the work in 1906, and it 

 was found so good as to warrant translating 

 into English by Mr. W. H. Story. There are 

 twenty-six chapters and profuse illustrations. 

 The greater portion of the book is naturally 

 devoted to balloons. These vessels have now 

 been developed to almost adequate speed and 

 efficiency in the " dirigible air-ships " of the 

 present day and the European nations are 

 providing themselves with war aerial navies 

 which are described and illustrated by Cap- 

 tain Hildebrandt, in a popular way so as not 

 to repel untechnical readers. 



He begins with the early history of the art, 

 this referring chiefly to flying machines, and 

 then gives two chapters to the hot-air balloon 

 and its subsequent supersession by the hydro- 

 gen balloon. In the fourth chapter the theory 

 of its flotation is taken up and formulse are 

 given for calemlating the " lift " at difierent 

 heights, or with different atmospheric pres- 

 sures. Also for the effects of temperature 

 upon the enclosed gas. Then four chapters 

 contain the history of the dirigible balloon, 

 with copious illustrations of the vessels which 

 have marked the gradual increase in speed. 

 This was twenty-two miles an hour for the 

 French "Lebaudy" in 1906. Since then it 

 has been increased by increased sizes to about 

 thirty miles an hour, which must be very near 



