548 



The Museum Gazette 



they were taken out and used as wanted, and might be kept 

 frozen for an indefinite time, and be alive when thawed in 

 cold water. The two pieces of a fish, cut in two when frozen, 

 would move and try to swim when thawed in cold water. " 



Air may be saturated with water-vapour and yet remain 

 clear if the air is perfectly dust free, for water-vapour requires 

 some nucleus on which to condense as a drop. If by any 

 means air thus saturated be rendered conductive to electricity 

 immediately a cloud is formed. " There is always and every- 

 where a difference of electric potential between the air and the 

 earth, which increases with the height. The earth is usually 

 negative and the air positive, but there are local and tem- 

 porary exceptions to this rule when the condition of these is 

 reversed ; for instance, during cloudy weather and rain." 



Late one summer evening two windows which opened out- 

 wards and were wide open became covered with moisture on 

 one side. The panes of those which were shut remained quite 

 dry on both surfaces. What was the cause of the difference ? 



The growths to which we have ventured to* give the ver- 

 nacular designation of " Witches' Scrubbing Brush " (see 

 p. 528) may be found on oak trees everywhere. We possess 

 a certain amount of evidence in support of the belief that they 

 are caused by gall insects, and would invite the co-operation 

 of our readers in determining the point during the ensuing 

 spring months. They should be watched from week to week. 

 The flies which are suspected are Aphilotrix mdicis and 

 Tvigonaspis crustalis, and maybe expected to make their attacks 

 in April. 



(Continued on p. 567.) 



