Oct. 1, 1S66.] 



HARDWICKE'S SCIENCE-GOSSIP. 



217 



CONSEBVATISM. 



" Conservatism— The practice of resisting changes; or of maintaining and preserving that which is established." 



Craig's English Dictionary. 



H E old adage de- 

 clares that "it is 

 always safe to 

 learn, even from 

 an enemy." This 

 is a statement 

 •which has received 

 many remarkable 

 illustrations in the 

 history of man's relations to 

 the globe on which he dwells. 

 In his contests with nature — 

 the contest of human will 

 with physical law — he has 

 committed many a grievous 

 error, and sustained many a 

 crushing defeat, through 

 ignorance of the truth that 

 in order to conquer nature 

 he must obey her. To speak 

 more accurately, it is only 

 by a careful study of natural 

 phenomena that agencies, 

 apparently adverse, can be 

 rendered subservient to the interests of mankind. 



In many parts of the world a struggle for ter- 

 ritory is going on, as real as, though, happily, far less 

 destructive than those which of late have crimsoned 

 the fair fields of Continental Europe. Take, for 

 example, the oases of the Algerian desert. The Arab 

 villagers are here constantly engaged in repelling the 

 assaults of the encroaching sands. These, urged 

 onward perpetually by the prevailing winds, would 

 speedily blot out all traces of cultivation were it not 

 for the unremitting labours of the native tribes. 

 Where resistance is not offered, the invading drift 

 carries on with alarming speed the work of deso- 

 lation. 



But operations of a more interesting character 

 are taking place on many of those belts of sand 

 No. 22. 



which divide sea from land, and form a neutral 

 territory, which is the subject of continual change. 

 Under certain conditions, the sands which under- 

 lie the waters of the ocean, and have been formed 

 either by agencies no longer in operation, or by 

 running waters and other existing phenomena, 

 heap up dunes or hillocks, and ridges along the shore. 

 This apparently simple process is thus analysed by 

 Jobard: "When a wave breaks, it deposits an 

 almost imperceptible line of fine sand, the next 

 wave brings also its contribution, and pushes the 

 preceding line a little higher. As soon as the 

 particles are fairly out of the reach of the water, 

 they are dried by the heat of the burning sun, and 

 immediately seized by the wind and rolled or borne 

 farther inland. The gravel is not thrown out by 

 the waves, but rolls backward and forward until it 

 is worn down to the state of fine sand, when it, in 

 its turn, is cast upon the land and taken up by the 

 wind." This ordinary action is of course greatly 

 intensified whenever a storm arises from the sea. 



The sand, thus transferred from the control of 

 the waters to that of the air, is urged forward 

 by the breezes, and rolled up the gentle ascent 

 of the shore, until plants, pebbles, or other slight 

 obstructions arrest its course, and permit the ac- 

 cumulation of a heap. In this way an irregular 

 line of somewhat conical hillocks is formed, which 

 may reach a height of even 5 or 600 feet. By the 

 same agency a second row of dunes is built up 

 within the first, and then a third and a fourth, until 

 these natural ramparts may form a belt of fortifica- 

 tions several miles in width. Thus does the ocean 

 rear mighty and effectual barriers against its own 

 incursions. 



But " Forwards !" is as truly the motto of the 

 sand-dune as ever it was of old Marshal Blucher, 

 and the hillocks of the shore may become as for- 

 midable invaders as the sand-waves of the desert. 

 The blown dunes advance landward often at a rapid 



