WEIGHING SCALE 



6240 



WEIGHING SCALE 



weevil, causes the p: in the United 



States (see BOLL WEEVIL). 

 The grain weevil is dark red and about one- 

 of an inch long. It is ructive 



FOUR OF THE WEEVILS 



in) Cotton boll weevil ; (b) full-grown larva of 

 (t: (c) cowpea weevil; (d) larva of same en- 

 larged. 



to wheat, laying its eggs on the wheat after it 

 is stored. The grubs burrow into the grain. 

 The rice weevil destroys rice and corn in a simi- 

 lar manner. The 

 alfalfa weevil first 

 appeared near 

 Salt Lake City 

 about 1904 and 

 has spread so 

 rapidly that it ALFALFA WEEVIL 

 yearly causes great loss in the alfalfa-growing 

 regions. It is a small, tawny-colored beetle, 

 less than one-fourth of an inch long. This bee- 

 tle was imported into the country from Europe 

 and Asia, where numerous insect enemies which 

 live upon the weevil and its eggs keep it in 

 check. The United States Department of Agri- 

 culture has imported these parasites in large 

 numbers, hoping that they will check the rav- 

 ages of the alfalfa weevil. 



There are numerous sorts of fruit weevils. 

 Some attack plums and cherries, the worms 

 feeding upon the fruit, which falls off or be- 

 comes wormy; others damage the strawberry 

 crop by attacking the blossoms, and the grape 

 weevil damages vineyards by attacking the 

 vines. W.F.R. 



Consult Comstock's Manual for the Studi/ of 

 Insects; Kellogg's American Insects. 



WEIGHING, wa'ing, SCALE, a mechanical 

 device for determining the weight of any sub- 

 stance. There are many forms of these ma- 

 chines, but they are all based on the principle 

 that certain weights balance each other or that 

 one will outweigh the other. Two pieces of iron 

 weighing exactly one pound each, if suspended 

 by two strings attached to each end of a bal- 

 anced and pivoted rod will not disturb the bal- 

 ance of that rod. If, however, the weights are 

 not equal, the heavier will pull its end of the 

 rod down and raise the lighter weight. If the 



rod is not exactly balanced, but pivoted at a 

 point nearer one end than the other, it would 

 require a greater weight suspended from the 

 shorter end to raise the pound suspended at 

 the longer distance from the pivot. There lies 

 the principle of the lever, on which most scales 

 are operated. 



The balance and the steelyard, the most fa- 

 miliar and simple forms of weighing scales, are 

 described in these volumes. Another familiar 

 form of weighing machine is the platform scale, 

 which consists of a hinged platform, set within 

 or above a fixed platform and pressing on a 

 lever underneath when a weight is placed on 

 it. The lever is connected with a rod which 

 rises perpendicularly for a certain height (ac- 

 cording to the size of the machine) and then is 

 carried at right angles to a point at which it is 

 pivoted, from which point it is continued in 

 the form of the longer end of a lever, with the 

 weights marked on it. The object on the plat- 

 form whose weight it is desired to know presses 

 down the lever under the platform, pulling 

 down the shorter end of the weighing lever and 

 causing the longer arm with the weights to 

 rise. A weight is moved along the lever until 

 an exact balance is found. The mark in pounds 

 indicated on the lever is the weight of the ob- 

 ject on the platform. 



In platform scales for weighing small quan- 

 tities the lever is made of such a length that 

 the weight of one pound on the lever may be 



7 



PRINCIPLE OF THE WEIGHING SCALE 

 A load is placed in the platform abed. Tin's 

 load is conveyed to the system of lexers by the 

 standards /, .</. /. /, and depresses them so that 

 they exert a pull downward on the rod km and the 

 short arm of the lever mp. This pull is bal;mrrd 

 by sliding the weight along the lever or scale beam 

 inn, which is so graduated into pounds and frac- 

 tions that the weight of the article on the plat- 

 form is read at a glance. 



equal to ten pounds or 100 pounds on the plat- 

 form. For weighing loaded wagons and trucks 

 this proportion may be increased until one 

 pound on the lever equals 1,000 pounds or more 

 on the platform. 



