366 RECENT PROGRESS IN PHYSICS. 



1. A column of water enveloping the thread immediately passed 

 between the glasses, and the silk thread was quickly drawn over from 

 the glass connected with the negative pole into the one containing 

 the positive pole, or that which led into the ground. 



2. After this had taken place^ the column of water continued for 

 a few seconds sus})ended between the glasses without the support of 

 the thread, and when it broke, the electricity passed in sparks. 



3. When one end of the silk thread was fastened in the negative 

 glass, the water diminished in the positive glass and increased in the 

 negative ; showing apparently that its motion was opposed to that of 

 the thread when free to move. 



4. By scattering particles of dust upon the surface of the water, it 

 was ascertained that two opposite currents passed between the glasses : 

 an inner one from the negative to the positive, and an outer one, en- 

 closing the other, from the positive to the negative. Sometimes the 

 outer current did not pass over into the negative glass, but trickled 

 down on the outside, and then the water did not increase in the nega- 

 tive glass, but diminished in both. 



5. After many fruitless attempts, the water was made to pass from 

 one glass to the other for several minutes without the help of a thread. 

 At the end of this time, no material variation in the quantity of water 

 in either of the glasses could be detected. Hence it appears that the 

 two currents were nearly, if not exactly equal, when the inner one 

 was not retarded by the friction of the thread. 



For the success of these experiments, it is essential that the water 

 should be chemically pure. The least im})urity caused the water to 

 boil on the thread, which, becoming nearly dry, is destroyed by the 

 heat developed by the current of electricity. 



Other chemical ejffects, such as the precipitation of copper, from its 

 solutions, upon silver, the decomposition of iodide of potassium, &c., 

 were well shown by this electrical machine. 



Finally, the electricity developed by steam, when conducted through 

 a coil of wire, deflected the magnetic needle and magnetized a cylin- 

 der of soft iron. 



§ 10. The source of atmospheric electricity still unknown — .Long 

 ago Volta and Saussure expressed the opinion that the atmos])heric 

 electricity might have its origin in the evaporation of water, and sup- 

 ported this view by experiments showing the development of elec- 

 tricity by evaporation. Their experiments, however, did not always 

 give constant results. The source of this uncertainty seemed to have 

 been discovered by the investigations of Pouillet ; according to his 

 experiments, the development of electricity does not take place on the 

 evaporation of pure water, but on the evaporation of water holding in 

 solution salt, acid, or alkalies. 



In the first edition of my work, based on Pouillet' s Physics, these 

 experiments are noticed on page 521 of the first part. Even then 

 these experiments did not appear to me to be conclusive; they seemed 

 to have been made without following the precautions necessary to the 

 establishment of FouiUet's views beyond doubt ; and hence I was led 

 to conclude the paragraph with the expression of the hope that a crit- 

 ical revision of these experiments might be made. In the later edi- 



