7 i8 



POPULAR SCIENCE MONTHLY. 



toward the circumference. This motion is 

 supposed to be caused by the great daily 

 change in temperature, often amounting to 

 80, and an unequal upward motion of the 

 mass below, increasing toward the center of 

 the lake. A few patches of shallow earth 

 lying on the pitch and covered with bushes 

 and small trees are scattered over the sur- 

 face of the lake. 



Nature's Landscape Gardening. A curi- 

 ous and interesting and yet easily explain- 

 able phenomenon is mentioned in a recent 

 paper by N. F. Drake, in the Journal of Ge- 

 ology, on The Topography of California. In 

 assisting to map a number of sand-dune 

 areas along the coast in San Luis Obispo 

 County it was noticed that where the sand 

 was free from vegetation or obstruction it 

 was piled in ridges at right angles to the 

 prevailing sea breezes; but that where 

 patches of vegetation grew, the dunes be- 

 came parallel to the direction of the wind, 

 and where the vegetation became thicker 

 over the ground the regularity of the ar- 

 rangement of the dunes was more broken. 

 The reversal of the direction of the ridges 

 where patches of vegetation existed was 

 accounted for as follows: A mass of grass 

 or bushes once started would check the sand 

 from moving at that point and make a shelter 

 for deposits to the leeward. This point of 

 the sand dune now being more stable, other 

 plant growth would spring up mainly on 

 the leeward side, so as to lengthen and 

 increase the elevation of the ridges, while 

 the unprotected sands at either side would 



drift away, thus forming narrow parallel 

 ridges in the direction of the prevailing 

 winds. Ridges from fifty to seventy- five feet 

 high and four to six hundred feet long, or 

 even longer, were not uncommon where the 

 sand dunes were extensive. 



Pegamoid. Pegamoid is a substance of 

 similar composition with celluloid, possess- 

 ing its desirable qualities, while it is not in- 

 flammable and does not lose shape when 

 heated. It was discovered by an English 

 lithographer seeking a means of protecting 

 the posters of his making from injury by 

 the atmosphere. Its composition is a secret, 

 but it appears to contain a nitrified cellulose, 

 alcohol, and camphor, or the essential con- 

 stituents of celluloid, together with some sub- 

 stances intended to increase its impermeability 

 and make it supple and uninflammable. It 

 may be applied in thin varnishes to any mate- 

 rial cloth, leather, paper, etc. so closely 

 that it can not be separated by any mechanical 

 means, and so as to form an impermeable 

 coating, easily cleaned by washing, and proof 

 against heat, grease, and alkalies, while it 

 has the further property of communicating 

 its qualities to the material to which it is 

 applied without destroying its individuality. 

 Pegamoid cloth is a cotton fabric covered 

 with a suitable thickness of pegamoid and 

 gauffered. The process of manufacturing it 

 is very simple, and consists in dyeing the cloth 

 in the desired color, mechanically coating it 

 with colored pegamoid, and stamping it. This 

 is only one of the innumerable applications 

 of which pegamoid is capable. 



MINOR PARAGRAPHS. 



The method of reproduction of the eel, 

 long a puzzle in zoology, has been discov- 

 ered. Young eels were known, but at too 

 advanced a stage of development to give any 

 clew to their primitive or larval state, and 

 no eels in this condition had ever been 

 recognized. Theodore Gill suggested in 1864 

 that larval eels might be identified with the 

 Leptocephalus, an animal which is found on 

 the British shores, in the Mediterranean, and 

 on the surface of the water in various parts 

 of the world. It has a body several inches 

 in length, thin, and of uniform width, like 

 a piece of ribbon, transparent, and unpig- 



mented. Professor Gill's suggestion was 

 verified by the investigations of Yves De- 

 lage in 1886 and Grassi and Calandruccio in 

 1892 and 1893, who showed that two spe- 

 cies of Leptocephalus were larvae respect- 

 ively of the conger and the common eel. 

 Fuller accounts of the observations of Pro- 

 fessors Grassi and Calandruccio have been 

 published recently in the Proceedings of the 

 Royal Society and the Quarterly Journal of 

 Microscopical Sciences. The specimens in- 

 vestigated were captured, along with deep- 

 sea fishes, in the Strait of Messina, where 

 the currents are strong and beset with whirl- 



