134 Mr 0. Fisher, On the condition [Jan. 29, 



January 29, 1894. 

 Prof. T. McKenny Hughes, President, in the Chair. 

 Mr E. W. MacBride was elected a Fellow of the Society. 

 The following Communications were made to the Society : 



(1) Electricity of Drops. By Professor J. J. Thomson. 



(2) Mr Griffiths described an easy method of making 

 absolutely air-tight joints between glass and metal tubes, by 

 means of an alloy which has a low melting-point. The use of 

 this alloy was suggested by Mr F. Thomas. An illustration was 

 given of the ease and certainty of the method. 



(3) A compensating open-scale barometer was then exhibited 

 and described by Mr Griffiths. 



The principle of this instrument is the same as that of 

 Professor Callendar's long-distance air thermometer. An air bulb 

 is placed within a second bulb and the annular space between 

 them is filled with sulphuric acid. The air and the H^SO^ have 

 a common surface in a tube connecting the two bulbs, the H^SO^ 

 also communicates with the air by means of a vertical tube 

 partially filled with acid. The masses of air and sulphuric acid 

 are so adjusted that when the temperature of the instrument is 

 raised, the increase in pressure due to the increased length of 

 the sulphuric acid column in the vertical tube exactly counter- 

 balances the increase in pressure of the contained air and thus 

 the position of the common surface is unchanged by alterations 

 in temperature, although at once affected by alterations in the 

 external pressure. The resulting scale is about six times as open 

 as the scale of a mercury barometer, and the readings give the 

 pressure expressed in terms of the length of a column of mercury 

 at 0" C. in latitude 45", without any preliminary calculations. 



(4) On the condition of the interior of the eai^th ; a correction 

 and addition to a fortner paper. By Mr O. Fisher, Hon. Fellow 

 of Jesus College. 



I wish to correct an error in a paper " On the hypothesis of a 

 liquid condition of the earth's interior in connection with Professor 

 Darwin's theory of the genesis of the moon," read in May last 

 year. It is unnecessary to go into all the geological arguments 

 which favour that view. Many of them will be found well set 

 forth in an article in the Fortnightly Revieiv^ by Dr Alfred 

 Russel Wallace, F.R.S. The strongest argument on the other 

 side is admitted to be the existence of ocean tides ; and it was in 

 1 Nov. 1892, "Our Molten Globe." 



