SOLAR SYSTEM 



5433 



SOLDIERS' HOMES 



tube. The object to be magnified is placed on 

 a stage at the opposite end of the tube. The 

 tube is attached to the inside of a closed win- 

 dow shutter, being placed over a hole. A 

 double-convex lens collects and brings to a 

 focus on the object the light rays, and by 

 means of a second lens a magnified image of 

 the object is projected on a white screen. 

 Modern instruments usually make use of the 

 electric arc or oxyhydrogen limelight instead 

 of the sun's rays. The solar microscope is 

 similar to a stereopticon (which see). 



SO'LAR SYS'TEM. When you hear some- 

 one speak of the sun as "Old Sol" you gain 

 the impression of a friendly relationship, as 

 though the huge ball of fire in the skies were a 

 man to whose faithful care we owe our light, 

 our heat, and an even more valuable posses- 

 sion, the genial sunniness of heart which we 

 feel on pleasant days. There are a great many 

 members of "Old Sol's" family the solar sys- 

 tem, as it is scientifically called for our own 

 earth is but one of countless bodies that travel 

 round and round him, receiving and reflecting 

 his light and heat in greater or less quantities 

 according to their nearness to or distance from 

 him. First of all, there are the eight large 

 planets, of which our earth is fifth in size; 

 next there are the smaller planetoids, or as- 

 teroids, which are counted in hundreds; lastly 

 there are the myriads of meteors, which travel 

 in swarms and are so small that they are not 

 visible unless they come in contact with our 

 atmosphere, whereupon they burst into flames 

 and are seen as shooting stars. Besides all 

 these there are the comets "visitors from 

 space," one astronomer calls them some of 

 which are "transients." 



None of the members of the solar system 

 moves about the sun in an exact circle, though 

 all have regular orbits. When the distance of 

 any one from the sun is stated, its mean dis- 

 tance is meant. A peculiar thing about the 

 distance of the larger bodies, first shown to the 

 astronomical world in 1722 by a German named 

 Bode, may be seen in the following table : 



Mercury 



Venus 



Earth 



Planetoid Eros 

 Mars . 



Planetoid Ceres 



Jupiter 



Saturn 



Uranus 



Neptune ,. 



Tens of millions Bode's 



of miles from sun numbers 



3.57 4 



6.72 7 



9.29 10 

 13.55 



14.15 16 



#7.66 28 



48.33 52 



88.60 100 



178.19 196 



279.16 388 



Bode formed his series of numbers by adding 

 4 to each number in the series, 3, 6, 12, 24, 48, 

 96. In his day the planets and planetoids 

 italicized in the above table were unknown, 

 but it was seen that the distances of six known 

 planets corresponded very closely to his num- 

 bers. In 1781 Uranus was discovered, and was 

 found to correspond fairly well with another 

 number in the table. Astronomers began to 

 take more interest in Bode's Law, and their 

 search for a planet to correspond to the missing 

 number 28 resulted in the discovery of Ceres 

 and other asteroids. Whether or not the law 

 is a mere coincidence or represents a true law 

 of the universe scientists do not yet know. 



Related Subjects. More about the solar sys- 

 tem will be found under ASTRONOMY, and certain 

 theories as to its origin in the article NEBULAR 

 HYPOTHESIS. The reader may also consult the 

 following articles : 



Asteroids Planet (with list) 



Comet Planetoid 



Copernicus Satellite 



Gravitation Sun 

 Meteors 



SOLDERS, sod' erz, alloys used to join sur- 

 faces or edges of certain metals, by fusion at 

 the point of contact. To be effective, a solder 

 must melt more easily than the metal to which 

 it is applied. Solders are of two classes hard 

 and soft. Hard solders are usually prepared 

 by combining in each case the metal to be 

 soldered with some others. Solder for gold, 

 for example, is prepared from gold and silver, 

 or from gold and copper, or from a mixture of 

 the three metals. Silver solder consists of 

 equal parts of silver and brass, with the addi- 

 tion of a little zinc. Soft solders are prepared 

 from varying proportions of tin and lead, bis- 

 muth being sometimes added. Hard solders 

 can be drawn out into threads and hammered 

 into sheets. That is, they are both ductile and 

 malleable. Soft solders melt the more easily 

 but are too brittle to bear hammering. Be- 

 fore surfaces are soldered they must be bright 

 and clean and free from oxide. 



SOLDIERS' HOMES, homes for disabled or 

 aged soldiers of the armies of the United 

 States. These homes afford provision for the 

 comfort and well-being of soldiers who have 

 lost their health in the country's service. Can- 

 didates for entrance into homes must be pro- 

 vided with an honorable discharge from service 

 and a medical certificate, which must show a 

 state of health which unfits him for ordinary 

 labor. Inmates are subject to the Articles of 

 War as if still serving in the army, and they 



