•m 



Mr. P. E. Shaw : 



Here is another, and a striking, instance of the baneful 

 effects of condensed water so well-known in electrostatical 

 work and in producing corrosion on mercury and other metals. 



Until the deleterious effect of damp had been fully appre- 

 ciated and the remedy understood, the observations taken for 

 days in succession were erratic and incomprehensible, if the 

 weather was at all damp. Two short tables will be given to 

 illustrate the effects of dampening the contact artificially. 



Tables I. & II. 



When there is no sticking the current required to make and 

 break contact is practically the same ; this is seen at the head 

 of each table. But when the contact is dampened, adherence 

 at once occurs. 



Remarks. 



Resistance to 

 overcome 

 torsion. 



Resistance to 

 overcome 

 sticking. 



A dry day. -> 

 Contacts cleaned. J 



3040 



3000 



3040 



3000 



Breathe on once — =*• 



3070 



500 





3070 



2500 





3070 



2700 





3070 



2700 



Contacts changed ... 



2940 



2920 





2940 



2920 



Breathe on once— *. 



3000 



1000 





3100 



2C00 





3100 



1500 





3100 



1500 



Before leaving this pseu do- coherence two more tables will 

 be given. In Table III. the gradual increase on the contact 

 of water from the air, with the accompanying adherence, can 

 be traced. The effect is small but quite distinct. In Table IV. 

 it is seen that water at the contact can be quickly dissipated 

 (by heating and electrolysis) due to a passage of a moderate 

 current. 



