

i8 7 i.] 



Meteorology. 



123 



Fig. 



the battery be in or out of use, the consumption of the sulphate of copper goes 

 on very nearly the same. When one firm alone sends out £10,000 worth of 

 sulphate of copper per month for telegraphic use at home or abroad, the value 

 of any invention which will prevent waste of this salt in the batteries may 

 very readily be judged. 



The improved form of battery is shown in Fig. 31. The great object to be 

 achieved is to stop the sulphate of copper, k, from 

 reaching the zinc plate, z, by diffusion. This is 

 effected by placing the copper salt in a compartment, 

 k, which is watertight at the sides and bottom of the 

 partition r. Thus the strongest part of the sulphate 

 w of copper solution lies at the bottom of the compart- 

 ment, k, and only the weakest part diffuses over the 

 top of the partition r. The level of the solutions in 

 the battery is represented by w w. Another water- 

 tight partition, b, is so fixed that the electrical 

 current has to pass through the diaphragm of wet 

 sawdust, e. This sawdust is well soaked in sulphate 

 of zinc before it is placed in the cell, therefore, it 

 remains at the bottom of the cell, and does not float on the surface of the 

 liquid. In charging the battery the compartment z is filled with weak sulphate 

 of zinc, and the compartments p and k with water. The copper plate, k k, has 

 a band of copper, n, attached to it ; the electro-deposit of copper begins on the 

 top of this plate, and very slowly spreads downwards. 



When the battery is not in action, the weak solution of sulphate of copper 

 diffuses into P, but when the battery begins working again, the copper is driven 

 back, and the liquid in p becomes once more colourless. Although there are 

 convection currents in the iiquid, the fad that the cell is divided into three 

 parts prevents these currents from carrying the sulphate of copper to the zinc 

 plate. 



The result of all this is, that the zinc plates are found to work away till they 

 become as thin as paper, and drop off the connecting band. The battery will 

 go on working for nine or fourteen months when employed in ordinary 

 telegraphic purposes, and it requires no attention beyond charging afresh about 

 once in three months. Some of these batteries have just been ordered by the 

 Government for trial. 



METEOROLOGY. 



Meteorology was fairly well represented at the British Association. The 

 Report of the Rainfall Committee contained a notice of some experiments 

 carried out at Calne by Colonel Ward, with the object of determining the 

 difference in the amount of rain collected at various heights above the ground. 

 The results of these are not in accordance with former theories. For instance, 

 we may take the comparison of the quantities collected on the ground, and at 

 a height of 20 feet above it, from which it appears that the difference is nearly 

 three times as great in winter as in summer, so that the mean annual cor- 

 rection is only applicable to the total yearly fall, separate coefficients being 

 required for the several months. 



A paper was read by Mr. Charles Chambers, of Colaba Observatory, Bombay, 

 on the cause of the variations of rainfall just alluded to, which he thinks is to 

 be found in electrical action. He supposes that the globules of water are 

 polarised by induction from the ground, and that according as they coalesce 

 drops are formed. This action would be most rapid close to the ground : it 

 would also be more active over vegetation than over bare earth, and it would 

 be stronger on hills than over plains, owing to the greater electrical tension on 

 the summits. 



Mr. F. Galton read a very ingenious paper on " Barometrical Predictions of 

 Weather," based on a comparison of the continuous records from Falmouth, 

 published in the " Quarterly Weather Report of the Meteorological Office." The. 

 result at which he arrived was, that if we use the ordinary rules given in the 

 text-books for barometrical fluctuations, and the indications of weather they 



