Branley Quadrant Electrometer, 1878

Consisting of a fine metal wire, a very light aluminum foil disc between four fixed brass sectors, a small mirror attached to the bottom of the suspended sector and a brass plate and the bottom of the wire in a Leyden jar for a solution of sulfuric acid, in a glazed brass case on mahogany baseplate with 3 leveling screw feet, a high glass tube on top of the case, overall height 27 ½ in. - Note: Thomson electrometer, built and modified by Bourbouze on the instruction of Professor Edouard Branly. Used mainly for various experiments with low currents, precursors to the discovery of wireless telegraphy (later called coherers). - A very rare and early scientific instrument, in good unrestored original condition.

布雷克拍品等级是为了方便竞买人判断拍卖品的成色而设置的。布雷克等级用1到6级来标注外观和功能的成色，(从非常好到非常差)。 在目录图册里用括号里的2个数字来表示，前一个数字表示外观成色的级别，后一个数字表示功能成色的级别。如(3/2)表示外观成色是3(满意的)，功能成色2(好)。 成色 定义参照下列标准： 1 - 非常好 (未使用过，没有使用痕迹) 2 - 好 (新，极少的使用痕迹) 3 - 满意的 (普通的使用痕迹) 4 - 及格的 (明显的使用痕迹，某个非主要部件是后配的) 5 - 有缺陷的 (极明显的使用痕迹, 某个主要部件是后配的，功能上有缺陷，需要修理) 6 - 非常差 (严重破损, 缺少重要部件)