SOKOTO 



5432 



SOLAR MICROSCOPE 



desirable soils for agricultural purposes. Loams 

 are classified as clayey, sandy, heavy or light, 

 according to their composition. Each is spe- 

 cially fitted to certain crops. 



Soils are coarse or fine according to their 

 texture. Fine soils are the more desirable for 

 agriculture, because they contain a larger pro- 

 portion of 'humus and also hold water better. 

 Each particle of soil is surrounded by a thin 

 film of water like that on a marble that has 

 been wet. This is the water used by growing 

 plants. Free water drowns the roots and pre- 

 vents them from absorbing nourishment, so 

 that plants die where there is too much water. 

 Since clay holds water, a certain proportion 

 of clay as necessary to fertility. Sandy soils 

 are infertile, because they do not hold water 

 and because they usually lack the necessary 

 proportion of humus. This may be supplied in 

 a measure by fertilizers. W.F.R. 



Consult Brooks's Soils and How to Treat 

 Them; King's The Soil; Hopkins' Soil Fertility 

 and Permanent Agriculture; Snyder's Soils and 

 Fertilizers; Hall's Soils. 



Related Subjects. The reader who is inter- 

 ested in a study of soils will find much that is of 

 interest in the following articles in these volumes : 

 Agriculture Loam 



Clay Loess 



Drainage Manures 



Dry Farming Marl 



Erosion Phosphates 



Fertilizer Rotation of Crops 



Irrigation Sand 



SOKOTO, so'kotoh, an important state 

 forming part of the British protectorate of Ni- 

 geria, in the west-central Sudan country, North 

 Africa. It borders on the Sahara Desert, and 

 in the northern part consists of arid lands, be- 

 coming more fertile, however, in the southern 

 portion. It covers an area of over 100,000 

 square miles and has a population estimated at 

 10,000,000. The chief town is Sokoto, with a 

 population of 10,000, but the most important 

 commercial center is Kano. 



The chief industries are agriculture and cat- 

 tle raising, the cattle being exceptionally fine, 

 though subject to great loss through plague. 

 The production of coffee is increasing, but the 

 principal products are hides, barley, millet and 

 wheat. British courts of justice have been es- 

 tablished, and the country is being opened to 

 large foreign commerce. Ostrich farming has 

 been introduced, and gives promise of being 

 eventually successful. Occasional rebellions 

 against British influence occur, but are usually 

 put down without serious trouble. 



SOLANUM, sola'num, the typical and most 

 important genus of the nightshade family of 

 plants. It includes herbs and shrubs of more 

 than 500 species, especially abundant in trop- 

 ical America. The most common and impor- 

 tant species is the common potato, and another 

 is the tomato. Other well-known species of 

 temperate regions are the bittersweet and the 

 common nightshade, which are widely distrib- 

 uted throughout America and Europe, and the 

 horse nettle and other spiny, troublesome 

 weeds native to the United States. Several 

 species, long ago used as medicine, are still 

 employed by the Chinese as medical remedies. 

 The fruits of many East Indian varieties are 

 eaten, and a species known as the kangaroo 

 apple is a common food in Australia and New 

 Zealand. 



Related Subjects. The following members of 

 the genus are treated in these volumes : 

 Bittersweet Potato 



Eggplant Tomato 



SO'LAR ENGINE, or SUN MOTOR, a me- 

 chanical device for collecting heat from the sun 

 and utilizing it as motive power. The name is 

 derived from the Latin solans, meaning sun. 

 The most successful solar motor yet invented 

 was erected at Pasadena, California, in 1901. It 

 consisted of a huge mirror in the shape of an 

 umbrella, thirty-six feet six inches in diameter 

 at the widest end, tapering off fifteen feet at 

 the bottom. The disk contained 1,788 small 

 mirrors, so arranged that the sun's rays might 

 be concentrated upon a boiler containing 100 

 gallons of water and space for eight cubic feet 

 of steam. The boiler was connected with ma- 

 chinery that pumped water at the rate of 1,400 

 gallons per minute. By an automatic arrange- 

 ment, as soon as steam was developed in the 

 boiler, the mirror was connected with clock- 

 work which caused it to turn with the sun in its 

 course. 



It was thought that the solar motor would 

 lead to great development of arid lands by 

 providing cheap means of running irrigation 

 pumps, but little has been accomplished in that 

 direction. The heat developed by solar motors 

 is intense. A solar motor, or burning mirror, 

 as called in England, developed heat which 

 melted a piece of iron in sixteen seconds. 



SO'LAR MICROSCOPE, mi'kroskohp, an 

 instrument for casting a magnified image of a 

 small object upon a screen by means of sun- 

 light or artificial illumination. It consists of a 

 brass tube and a reflecting mirror, so adjusted 

 that the rays of light are reflected into the 



