AN()IENT DESEMERS OR STEELYARDS. 563 



(xeniian desemers are used for, and quite another to wei^h out a 

 desired quantity of any commodity, which is the common problem of 

 the retailer. If it is desired to weigh a goose, or several tish in a net, 

 it can be done with a connuon desemer, with the reiiuisite skill. But 

 to weig-h out 5 pounds of pease with a desemer is a difficult task, indeed, 

 for none can be taken out or put in while the balance is in action, 

 because it does not oscillate at all, but simply '' upsets" as soon as the 

 departure from equilibrium is sufficient to overcome the friction 

 Now, since it was the custom in ancient Rome to use balances on the 

 principle of our desemers in shops, as the Clusium balance proves, it 

 follows that men were directly required to think out improvements 

 wherel)y the desemers, when loaded, should oscillate. Now the two- 

 pan balances made l)y the Romans were constructed essentially right. 

 The position of the axis of rotation was correct, which is the essential 

 condition for the oscillation of the balance. In order to make their 

 desemers oscillate, and so luake them practicable for shopkeepers, the 

 Romans inti'oduced the bridge above the pillar. The lower end of the 

 bronze handle from which the other piece hangs is quite above the 

 center of gravity of the latter, so that a fine oscillation and return from 

 every oblicpie position must have resulted. You can see how the 

 bridge works l)y simply attaching one made of wire to the common 

 (icrman desemer, when you see how much l)etter it works and how 

 well it oscillates. The ancient Romans, doubtless, attached that ugly 

 bridge to their beautiful balance just to cure it of that quite intoler- 

 a>>le fault. It looks like an excrescence upon the original design. 



If \ou ask why desemers so seldom are furnished with such bridges, 

 the answer is it is not the only requirement that a balance should oscil- 

 late; it uuL^t also be sensitive. It has already been remarked that 

 a good balance ought to have its point of support oidy a little above 

 the common center of gravity of the beam, the load (placed where 

 attached), and the counterpoise. The higher the point of support the 

 more the sensibility is lost.^ For example, this German desemer 

 leaves the horizontal position with an overload of one-fifth or one- 

 sixth of an ounce (5 or grams), but, with the ])ridge, it needs a])Out 

 half an ounce (15 grams) to give a perceptible turning. So it is with 

 the Clusium balance; it needs a third of an ounce to turn it percepti- 

 bly, so that it never could have answered for fine weighmg. In point 

 of sensibility, therefore, this l)alance left much to be desired. 



Whether "the Romans ever improved any further upon this type of 

 balance, or passed directly to the steelyard with the running weight, 

 or to this latter through the two-pan balance with a rider, sucn as has 

 been found in Pompeii, remains undecided. The sensibdity of the 

 Clusium balance certainly might have>een greatly i.K-reased witJiout 



' Fig. 17 8hmv^^7d^s^iu«Jr7vh^h inuHt combine nensibiiit y uitl) rapi.l weighing and 

 which certainly would not upwet, but would osc-illate.— Fr. 



