Here I have an apparatus for heating curling tongs by electricity; here is a flat iron treated in the same way, and here is a kettle in which the current is carried to boil water. I travel a good deal, and I always carry in my traveling bag a battery like this, which is one of Pitkin's secondary batteries; it is light and extremely convenient. I can strap it on my shoulder like an opera glass. To this is attached a reading lamp which I fix in my waistcoat, and to the astonishment of my fellow travelers, when the shades of evening are beginning to set, I take out the lamp and put it in operation--so. My reading lamp is thus provided, and it is fixed in the most convenient position, for the light falls just where it is wanted, it does not offend the eye, and enables me to read the smallest print. I have always got with me my own light, perhaps much to the annoyance of my fellow passengers, and with the electric light machinery at my own house, I have little or no trouble in recharging the battery, or keeping it in order. The Pitkin battery is also applied to a miner's lamp. EFFECT OF CHLORINE ON THE ELECTRO-MOTIVE FORCE OF A VOLTAIC COUPLE.[6] By D. G. GORE, F.R.S. If the electro-motive force of a small voltaic couple of unamalgamated magnesium and platinum and distilled water is balanced through the coil of a moderately sensitive galvanometer of about 100 ohms resistance, by means of that of a small Daniells cell, plus that of a sufficient number of couples of iron and German silver of a suitable thermo-electric pile (see Proc. Birm. Phil. Soc., vol. iv., p. 130), the degree of potential being noted, and sufficiently minute quantities of very dilute chlorine water are then added in succession to the distilled water, the degree of electro-motive force of the couple is not affected until a certain definite proportion of chlorine has been added; the potential then suddenly commences to increase, and continues to do so with each further addition within a certain limit. Instead of making the experiment by adding chlorine water, it may be made by gradually diluting a very weak aqueous solution of chlorine. [6] Read before the Royal Society, May 3, 1888. The minimum proportion of chlorine necessary to cause this sudden change of electro-motive force is extremely small; in my experiments it has been one part in 17,000 million parts of water;[7] or less than 1/7000 part of that required to yield a barely perceptible opacity in ten times the bulk of a solution of sal-ammoniac by means of nitrate of silver. The quantity of liquid required for acting upon the couple is small, and it would be easy to detect the effect of the above proportion or of less than one ten-thousand millionth part of a grain of chlorine in one tenth of a cubic centimeter of distilled water by this process. The same kind of action occurs with other electrolytes, but requires larger proportions of dissolved substance.