348 



Solar Spectrum. Secondary Batteries. 



[May 21, 



These spicules belong to numerous species. All four orders of 

 siliceous sponges are represented, but whilst the Monactinellid and 

 Hexactinellid sponges form but a small proportion, the Tetracti- 

 nellid and Lithistid sponges, more particularly those of the Mega- 

 morina family, are extremely abundant. 



III. " The Solar Spectrum from ^7150 to \10,000." By Capt. 

 Abney, RE., F.R.S. Received May 6, 1885. 



(Abstract.) 



The paper deals with the method employed in taking the photo- 

 graphs of the solar spectrum, from which the map accompanying it 

 was made, and indicates the degree of accuracy which has been 

 obtained. 



IV. " On Charging Secondary Batteries." By William Henry 

 Preece, F.R.S. Received May 6, 1885. 



1. I have for the past twelve months been experimenting with 

 secondary batteries with a view of getting an efficient, uniform, and 

 constant source of currents for electric lighting my house, and I have 

 succeeded beyond my expectations. Some new facts have developed 

 themselves during my experience, which I have thought of sufficient 

 importance to bring before the Society. 



2. The cells are of the Plant e type, manufactured by the El well 

 Parker Company of Wolverhampton. Fourteen plates of plain sheet 

 lead 17" X 11" are suspended in well insulated wood boxes filled with 

 diluted sulphuric acid in the proportion of about 1 to 10. These 

 plates are grouped in two groups of seven, each group being soldered 

 to a lead strip, forming alternately the positive and negative poles of 

 the cell. The plates of the respective poles are prevented from 

 touching each other by ebonite grids or separators.* Each plate 

 offers a surface of 1*3 square feet, so that the total surface of lead of 

 each group opposed to each other is 91 square feet; tjiat is, 9'1 

 square feet of peroxidised lead is opposed to 9'1 square feet of 

 spongy lead. I use twenty-four such cells. 



3. My charging current varies from 3 to 3J amperes per square 

 foot, while the current of discharge used in lighting my house varies 

 from 1 to 1 J ampere per square foot. The total weight of each cell is 



* These ebonite grids were introduced by Mr. Charles Moseley, and hare effec- 

 tually removed one incessant source of trouble in these cells, viz., short-circuiting 

 through the buckling of the plates. 



