160 TEAR-BOOK OF FACTS. 



zine, February, 1852) has shown that with a concentrated solution 

 of canstic potassa, he obtained with carbonic acid a vacuum with 

 the air-pump so perfect as to exercise no appreciable tension, as no 

 difference in the level of the mercury in the siphon-gauge could be 

 detected. On trying the discharge in the vacuum- tube after the 

 potash had cooled, Mr. Gassiot found it gave the cloud-like stratifica- 

 tions, with a slight reddish tinge ; consequently not only was the 

 vacuum not perfect, as denoted by the form of stratifications, but 

 in this tube the colour denotes that even a trace of the air remains, 

 probably that portion in the narrow part of the siphon-gauge, which, 

 from its position, was not displaced by the carbonic acid. 



The potash was subsequently heated until the discharge was reduced 

 to a wave line, with very narrow stria? ; in this state moisture ia 

 seen adhering to the sides of the tube ; but even in this condition the 

 difference in the level of the mercury in the gauge did nut ever vary 

 more than '05 inch. As the potash cooled, the discharge altered 

 through all the well-known phases of the stria?, the mercury agaiu 

 becoming quite level. At first almost the slightest heat applied to 

 the potash alters the form of the stratifications ; as the heating is 

 repeated, longer application is necessary ; but it shows how sensibly 

 the electrical discharge denotes the perfection of a vacuum, which 

 cannot be detected by the ordinary method of mercurial siphon- 

 gauge. 



CONDUCTIVITY OF COPPER. 



Professor Wiieatstone has communicated to the Royal Society 

 a paper prepared by MM. Matthiessen and Holzmann on the effect 

 of the presence of metals and metalloids upon the Electric- Con- 

 ductivity (or conducting power) of pure Copper. After numerous 

 experiments, and after studying the effects of sub-oxide of copper, 

 phosphorus, arsenic, sulphur, carbon, tin, zinc, iron, lead, silver, 

 gold, &c, on the conducting power of copper, the authors have 

 come to the conclusion that " there is no alloy of copper which 

 conducts electricity better than the pure metal." 



new secondary pile of great power, by m. g. plants. 

 Jacoi i has proposed the use of Secondary Electric Currents 

 for telegraphic purposes, and Plante has suggested tin; substitution 

 of electrodes oi lead for those of platinum in these batteries. A 

 more extended study has convinced him of their use. He .states that 

 a battery with electrodes of lead has 2\ tunes the eleotromotive 



force of one with electrodes of platinized platinum, and six tin 



great as that of one with ordinary platinum. This great power 

 From the powerful affinity which peroxide of lead has for 

 hydrogen, a fact first noticed by De la Hive. The secondary battery 

 which be reoommendi has the following construction : —It consists of 

 nine elements, pros cmting s total surface of ten square metn i. Each 



element IS formed of CWO Large lead plates, rolled into a spiral and 

 separated by coarse cloth, and immersed in water acidulated with 

 one-tenth sulphuric acid. The kind of current used to excite this 



