ON ATMOSPHERIC ELECTRICITY AT MADEIRA. 



63 



Absolute Thermal Conductivities obtained in a Defective and Underrating 



Condition op the Apparatus, 1879. 



Measures (in 1879), compared with Stefan's Determination (1876), to test 

 the Action of the Apparatus. 





Report of a Committee, consisting of Professor Gh Forbes, Professor 

 Sir William Thomson, and Professor Everett, appointed to 

 obtain Observations on Atmospheric Electricity at Madeira. 

 Drawn up by Dr. G-rabham, Madeira. 



One of the latest of Sir William Thomson's portable electrometers was 

 entrusted to me two years ago for taking electrical observations in 

 Madeira. I received no intimation as to any particular set of observations 

 which were thought desirable to take, and I have hence considered myself 

 "unfettered to seek out that which seemed most inviting and most likely 

 to yield new facts. 



The daily observations I discarded, finding them extremely monotonous 

 and irksome, and I think they are not likely to prove instructive at all, 

 unless a continuous record is made by automatic means. But it is ob- 

 vious that in so uniform a climate as tbat of Madeira, where calm fine 

 weather often lasts steadily for several weeks without a break, a station 

 for observing the diurnal and seasonal electric variations would be ex- 

 tremely valuable. 



_ I have, however, devoted whatever time I have been able to give to 

 this subject to the observation of the regular breezes and prevailing 

 winds. Early in the morning, in ordinary fine weather, there is no wind 



