682 



The author has no doubt that electricity, which accompanies each 

 radiation, acts positively under the influence of the one, and nega- 

 tively under that of the other, without changing the chemical com- 

 pound ; in the one case this influence would give the aflSnity for 

 mercury, and in the other it would destroy it. 



3. " On the Value of Absolute Alcohol in Spirits of different 

 Specific Gravities." By George Fownes, Esq., F.R.S., Professor of 

 Practical Chemistry in University College, London. 



Having been recently engaged in a series of experiments on the 

 fermentation of sugar and molasses, which rendered it necessary to 

 refer to a table of the value in absolute alcohol of spirits of different 

 specific gravities, the author found himself compelled to construct 

 for this purpose a new table, vvhich he lays before the Royal Society 

 in the present paper. 



The table was formed by weighing out absolute alcohol and di- 

 stilled vrater in fixed proportions, mixing them, and after allowing 

 time for condensation, determining with suitable precautions the 

 specific gravity of each mixture at the temperature of 60° Fahren- 

 heit. Each alternate number in the table was so obtained ; the rest 

 being interpolated. The alcohol employed was prepared by digest- 

 ing the strongest rectified spirit, first with dry carbonate of potash 

 and afterwards with powdered quicklime and distilling. It had the 

 specific gravity '7938 at 60°, and boiled at 177° Fahr. 



The table is followed by a diagram for the purpose of contrasting 

 the actual specific gravities found by experiment with the calcu- 

 lated mean specific gravities of the various mixtures of alcohol and 

 water, in' which the specific gravities are indicated by horizontal 

 lines and the proportions of the two liquids by vertical lines. The 

 mean specific gravities of course run straight across the diagram 

 from corner to corner, while the actual specific gravities form, an 

 irregular curve v»ith upward convexity, rising rapidly to near its 

 maximum deviation at SO per cent., proceeding nearly parallel with 

 the other line to 50 per cent., and thence declining until it reaches 

 the extremity of the scale. 



4. On the existence of alternating diurnal Currents of Electricity 

 at the Terrestrial Surface, &c., and tlieir connection with the Diur- 

 nal Variation of the Horizontal ?>Iagnetic Needle." By W. H. 

 - Barlow, Esq., M.LC.E. Communicated bv Peter Barlow, Esq., 

 F.R.S., &c. 



The observations recorded in this paper were undertaken in con- 

 sequence of certain spontaneous deflections having been noticed in 

 the needles of the Electric Telegraph on the ^Midland Railway. 

 The telegraph is constructed on the principle patented by Messrs. 

 Wheatstone and Cooke, and the signals are made by deflecting a 

 magnetic needle placed in a coil, to the right or left, by means of a 

 galvanic battery. It was observed that when no signals were pass- 

 ing, and when the wires of the telegraph had simply connexion 

 with the earth at the two termini, spontaneous deflections, differing 



