by Dr. Van Marum. 315 



111 experiments of the fame kind made with the hcdyfarutv 

 gyrdn$ t the electricity produced no acceleration nor retarda- 

 tion in the movement of the fmall leaves. 



10. Electricity produced variations in the flat e of the ba- 

 rometer, but only in a fmall decree when the mercury had 

 not been boiled, and when, of courfe, it ftill contained fome 

 moilture. 



11. An experiment was undertaken at the requeft of Volta, 

 to afcertain ivhether the evaporation of liquors at the common 

 leinperature of the aimofphere would be increafed by electricity. 

 — Doctor Van Marum firli placed water, alcohol, fulphurie 

 ether, accurately weighed in fmall porcelain cups, on a con- 

 ductor, and at the fame time fimilar quantities at fome di- 

 Itance from the machine. After being expofed to electricity 

 for half an hour, no figns of increafed evaporation could be 

 perceived. The cafe was the fame in other experiments 

 where the circumftanees were changed. Volta propoied alio 

 two other experiments ; one for , the purpofe of trying whether 

 electrified air be more impregnated with water than other 

 air, and, whether the atmofphere be rarefied by electricitv. 



12. On the reduction of metallic oxides by electricity . — As 

 this was effected in the year 1785 with fparks drawn from a 

 battery, Dr. Van Marum was defirous of trying whether it 

 -could be done alfo with fparks from a conductor; whether 



air was produced during each revival ; and if fo, of what kind. 

 For this purpofe he employed tubes like thofe already de- 

 fcribed in art. 5. The fparks were three inches in lens'th. 

 Red lead was almoft immediately revived, and, within 

 twenty minutes, there were produced about | cubic inch of 

 gas, 1 -3d of which was carbonic acid gas. The reiiduum 

 fhowed in the eudiometer not fo much decreafe as atmo- 

 fpheric air. White lead, treated in the fame manner, was 

 reduced in a lefs degree; lefs air alfo was produced ; but in 

 other refpeCts it appeared to be the fame. Oxide of tin was 

 not reduced, and, alter being electrified half an hour, gave no 

 air. The cafe was the fame with the oxide of iron. Oxide 

 of mercury prepared by heat was very foon reduced into the 

 form of very fmall globules, of a black colour, adhering to 

 * .the 



