204 N. ANNANDALE : 



weight arm is intentionally made much the shorter so that special weights of smaller 

 size can be used for convenience of manipulation, but the equal armed type is most 

 common. The swinging pans are inconvenient for many purposes, so special arrange- 

 ments are devised, using links and parallel motions in order that the pans may be 

 placed above the beam ; but it would be hopeless to pursue this part of the subject 

 into all its ramifications. 



In the ordinary steelyard, one arm is shorter and heavier than the other, and the 

 longer arm is generally graduated. Then either the weight slides along this graduated 

 arm as in fig. 4, or, more rarely, the pan, carrying the article to be weighed, is 

 moved along it as in fig. 5. In either case the position gives the measure. Some- 

 times removable weights are used alone or in combination, as in figs. 6 and 7, to give 

 the approximate weight while the slide is used to make the finer adjustment. 



As with balances, there are to be found all variations from the stick and string 

 type up to the reversible steelyard with two fulcra F 1 F 1 represented in fig. 11, which 

 can be used for weighing light or heavy articles within a limited range. 



Sometimes instead of a sliding or removable weight, a sliding telescopic arm with 

 graduations is used. Or a hinged weight, which can be folded over so as to lie nearer 

 to or farther from the fulcrum, is mounted on one side and then the instrument will 

 only give two measurements. A common form of coin-tester consists of a weighted 

 lever with recesses, properly spaced and sized in the longer arm to receive coins of 

 different denominations. 



At the best of times the steelyard is rather a clumsy instrument in its simpler 

 form. To use a colloquial phrase, it waggles about. So generally it is more con- 

 venient to mount it in a stand and connect it either directly or indirectly through 

 multiplying levers, to a platform on which is placed the article to be weighed. In 

 these forms the steelyard is utilised for weighing anything from a letter to a loco- 

 motive. The levers may be straight or bent but, if the latter, they are kept so nearly 

 in one position that there is no change of leverage as in the bent lever or pendulum 

 type considered under the next class. 



The sixth class, in which the distance of the weight and the article from the 

 fulcrum are simultaneously altered, embraces two main forms: — (1) the movable 

 fulcrum or bismer type fig. 8, and (2) the fixed fulcrum bent lever or pendulum type 



fig- 9- 



The bismer type, as Dr. Annandale has remarked, is found in several centres, but 

 is not nearly so widely spread as the balance or steelyard. For equal differences of 

 weights the lengths of the graduation vary, and are best found by actual tests Some- 

 times the fulcrum or suspension-point is moved along the beam ; at other times a 

 separate suspension-string is placed at each of the fulcra , and the weight is then deter- 

 mined by noting the particular string used as the support when the beam is level. 

 Many variations could be devised, and the writer ventures to suggest that the form 

 shown in fig. 12 is more or less novel. In this the beam is square and has four 

 fulcra, F 1 F 2 F 3 F + , one on each side ; but the beam might be round with a projecting 

 continuous spiral rib, to act as a fulcrum wherever it touches the support. By 



