VOL. LXXXI.] PHILOSOPHICAL TBANSACTXONS. 55 



It appears from this journal, that there were only 7 days throughout the year 

 in which no signs of electricity were perceived; viz. the 15th and 23d of No- 

 vember, and the 6th, 15th, 17th, 21st, and 22d of December, 



Remarks on the phenomena exhibited by the rod on the 3 1 st of August. Mr. R. 

 was for a long time extremely puzzled to account for the rapid changes which the 

 pith balls on some days so frequently exhibited ; being positive one minute, then ne- 

 gative for another, and the next returning again to positive. From often con- 

 sidering this apparently whimsical changeableness in nature, he was at length 

 induced to suspect, what indeed was afterwards confirmed by actual experiment, 

 viz. that some of these changes are only apparent, and not real, being occasioned 

 not by the actual communication of a different sort of electricity, but merely by 

 the action of electrical atmospheres. Thus, when an electrified cloud comes 

 within a certain distance of the rod, and before it comes near enough to impart 

 to it some of its own electricity, the electrical atmosphere of the former, agree- 

 able to the well known laws of electricity, will disturb the electric fluid naturally 

 belonging to the rod, and will consequently occasion several apparent changes in 

 the electrometer, which changes an unexperienced observer would attribute en- 

 tirely to the change of electricity in the clouds. This observation was confirmed 

 by the phenomena observed on the 31st of August; whence it appears, that the 

 real number of changes from positive to negative, or from negative to positive 

 electricity, cannot be so great as it is shown by tiie electrometer affixed to 

 the rod. 



XIII. Further Experiments relating to the Decomposition of Dep/ihgisiicated 

 and Injlammable Air. By Joseph Priestley, LL. D., F. R. S. p. 213. 



The doctrine of phlogiston, and that of the decomposition of water, have 

 long engaged the attention of philosophical chemists, and experiments have some- 

 times seemed to favour one conclusion, and sometimes an opposite one. I have 

 myself been very differently inclined at different times, as appears in my publi- 

 cations on the subject ; and I am hardly sensible of a wish which way this im- 

 portant controversy, as it may be called, be decided, notwithstanding the part 

 that I have taken in it. I cannot help thinking however, that the experiments, 

 an account of which I shall now lay before the society, are decisive in favour of 

 the composition of an acid from dephlogisticated and inflammable air; and there- 

 fore, that the opinion of these 2 kinds of air necessarily composing water, cannot 

 be well founded. It is indeed sufficiently evident, that the same elements also 

 compose fixed air, and therefore it is the less extraordinary that they should com- 

 pose another acid. 



The doctrine of phlogiston, I would however observe, will not be affected by 

 the most decisive proof of the composition of water from dephlogisticated and 



