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Page:Popular Science Monthly Volume 33.djvu/550

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THE POPULAR SCIENCE MONTHLY.

nearly the actual frequency of occurrence agreed with the theoretical average frequency.

We might mention, also, a number of parlor-games which involve some degree of muscular exercise; and others, like the game of twenty questions, which require vivacity and brightness in the use of language. But the main principles to which we wished to call attention have been sufficiently illustrated by the sedentary games and solitaires which we have already mentioned. The therapeutic value of a game depends upon its adaptation to the individual tastes and needs of the person who takes it up. It must be such as to interest him and keep his attention, and yet not such as to absorb, excite, and fatigue him. His native and acquired tastes, his age and habits of life, the state of his health, the causes of his fatigue, or of his illness—all these, and other similar causes, will influence the effect that any particular game or amusement will have upon him; and in the exercise of a sound common sense, by himself and his friends, he will select and vary his amusements as carefully as he selects his various occupations, or chooses his diet.

 

DRIFT-SANDS AND THEIR FORMATIONS.

FIVE large sand-tracts may be designated in Europe—the German lowland, extending from Holland through Germany to Russia (about 340,000 English square miles in area); the Dano-Germanic island plains (20,000 square miles), including Schleswig-Holstein, Denmark, and Jutland; the Austro-Hungarian Danubian plain (about 42,000 square miles); the Landes of France (about 5,400 square miles); and the sea-coast sands of Russia, Germany, Belgium, Holland, and France. These extensive regions have, for the most part, either been made amenable to cultivation, or at least protected from the assaults of the winds by preservative plantations. Tracts of this sort are often much more fruitful than we are accustomed to suppose them to be. But there are also in Europe large fields of sand which are hardly if at all covered with plants. They are the dunes and sands on the coasts of Prussia, Pomerania, Jutland, many of the Danish and Frisian islands, Hanover, Oldenburg, Holland, Belgium, and France. Large systems of dunes extend in France from Brittany to near the Pyrenees. But there are also exposed sand-tracts in the interior. The most extensive of them are in Hungary, of which the most important is probably the sand-barren of the Banat. It forms an oval about thirty-five kilometres long by eleven kilometres broad, and has an area of nearly four hundred square kilometres. It presents the appearance of a rolling region with elongated hills.