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of Edinburgh , Session 1875 - 76 . 
disadvantages mentioned under I. must be taken into the bargain, 
and, besides, the inherent precision of the balance gets less.* To 
pass to an example: What we gain by substituting a 7-inch for a 
14 inch bea,m is that, for the most convenient t, the sensibility 
becomes 2 to 4 times greater; but this advantage is secured with- 
out expense in good qualities by placing before the graduated 
limb a lens magnifying the excursions of the needle into 2 to 4 
times their natural size. This is the theory of the u short beams” 
which have lately come so much into fashion. 
To come back to my own balance, I must not forget to thank 
Messrs Becker Sons of Rotterdam for the readiness with which 
they have, at their own risk, tried to realise my ideas in an 
actual instrument, which, by the way, is now being exhibited at 
South Kensington. To increase the usefulness of the instrument, 
I have caused Messrs Becker to add to it a glass plunger, which 
is adjusted so that it displaces exactly 10 grammes of water at 
15°, and which consequently enables one with great rapidity to 
determine the specific gravities of liquids by tbe method of 
immersion. 
To pass now to the new gas- governor , its most essential part 
consists of a mercury-manometer (fig. 2), of which one limb. A, is 
about 20 mms. wide, and stands vertical ; while the other, C, is of 
the width of a thermometer tube, and is placed horizontally. 
* For fuller explanations, see my article “ Balance ” in the “ Encyclopaedia 
Britannica.” 
