436 



SCIENCE. 



[Vol. XIII. No. 331 



makes of lamps were used in the tests, their candle-power and effi- 

 ciency being determined at intervals during a working period of 

 850 hours. There were fifteen commercial lamps of each make at 

 first, but afterwards some additional lamps were sent from the fac- 

 tories. The methods of tests used were calculated to give accurate 

 results, and much care was taken in the measurements, there being 

 frequent comparisons of both current and potential measuring- 

 instruments with standards ; while the Methuen burner used in 

 determining the candle-power was compared with standard candles, 

 and found to be practically correct. 



The results of the measurements can hardly be regarded as 

 flattering to incandescent-lamp manufactures. The initial efficiency 

 of the lamps varied from about 3 watts to the candle-power (about 

 fifteen i6-candle-power lamps to the electrical horse-power) to 5 

 watts to the candle-power (nine lamps to the horse-power). As 

 time went on, however, the lamps, from the blackening of the 

 globes and the increased resistance of the filaments, grew dimmer, 

 until the candle-power had gone down in some cases to six or eight 

 candles ; while the efficiency had decreased, until in some cases 

 lamps which gave a candle-light with an expenditure of 3 watts, 

 finally required 7 watts to give the same light. The highest aver- 

 age efficiency for any make of lamps, for 800 hours, was 4.58 watts, 

 the lowest 5.8 watts, per candle-power. Probably the most satis- 

 factory of the lamps experimented on had an average efficiency of 

 -about 4.8 watts ; the final candle-power, after 900 hours' service, 

 Jjeing about 14, the initial being 16 candles. 



An important point brought out in these tests is the marked de- 

 crease in the candle-power of commercial lamps, even after a mod- 

 erate service. It is not at all satisfactory to consumers to have 

 the lamp gradually decrease in brightness until it finally does not 

 give enough light to read by, and to this cause may doubtless be 

 attributed the comparatively slow introduction of the light. If the 

 users are to replace the lamps, it is hardly in human nature to do 

 so until they are broken, and a life of 2,000 or 3,000 hours is not 

 uncommon. At the end of that time, a i6-candle lamp is giving 

 about six candles, and that at a very low efficiency. There are 

 many electric-light companies that guarantee twelve i6-candle 

 Samps to the mechanical horse-power (equivalent to an efficiency of 

 the lamp of about 3 watts to the candle). It is possible that a 

 plant might give such results for a few hours ; but, if these tests are 

 to be trusted, none of the lamps in extended commercial use can 

 do better than a candle-power for 4.8 watts, with the light at the 

 end of 900 hours having 85 per cent of its initial brilliancy. The 

 practical life of the lamp, then, is limited by two things, — the 

 breaking of the filament, and the decrease of candle-power. This 

 latter has not been recognized as it should have been, and Mr. 

 Peirce's paper is of value in calling attention to it. 



Inherent Defects. OF Le.4d Secondary Batteries. — A 

 paper under this title was read at the meeting of the Institute of 

 Electrical Engineers by Dr. Louis Duncan. It consisted mainly of 

 a description of and deductions from a series of experiments which 

 had been carried on by himself and Mr. Henry Wiegand during 

 the past year ; the principal points investigated being the loss of 

 ■energy in charging and discharging such cells, with the causes of 

 their deterioration. The cells experimented on were of the " grid " 

 type, in which the active materials — peroxide of lead and spongy 

 lead — are pasted into hourglass-shaped cavities in a cast-lead 

 "" grid." This type is the one almost universally used in commer- 

 cial work, and it has so far been the most successful. The defects 

 of these batteries lie (i) in the limited storage capacity, it being 

 but one-eighth of the calculated value ; (2) in the loss of energy in 

 charge and discharge ; (3) in the deterioration ; (4) in the low dis- 

 charge rate allowed by considerations of efficiency and length of 

 life. The loss of energy exhibits itself by two effects, — a lower 

 potential difference on discharge than on charge, and a loss in 

 ampere hours between charge and discharge. The loss of energy 

 must be traced to two things, — the production of heat or the 

 formation of irreversible chemical products. It is known that the 

 electro-motive force of a secondary battery is greater as the strength 

 of the acid increases. When the strength is greatly diminished, 

 there is a formation of irreversible sulphates of lead and a rapid 

 corrosion of the plates. It is also known that discharge of the cell 

 consists in a sulphating of both plates, causing a weakening of the 



acid ; charge results in desulphating, strengthening the acid. In the 

 plugs of active material, where diffusion is slow, there must be 

 considerable differences of density in the acid between charge and 

 discharge, this being especially the case when the current rate is 

 considerable. We can consider, then, that the charge is in strong 

 acid ; the discharge, in weak. To these considerations correspond 

 the facts that the electro-motive force is higher on charge than 

 discharge ; that a rapid discharge lowers the electro-motive force, 

 which, however, rises again after a period of repose ; and that a 

 rapid discharge causes a deterioration of the plates. To see if 

 there were any ground for these suppositions, experiments were 

 made on the rate of diffusion of acid from the plates, and it was 

 found to be slow, especially with partly run-down plates, this cor- 

 responding to the fact that fully charged plates can be discharged 

 more rapidly than partly discharged ones. To fix the losses of 

 energy which result in heat effects, a cell was discharged in a 

 calorimeter, and the rise of temperature and other data observed 

 under various circumstances. The first thing that appeared was, 

 that there was a much greater heating during charge than during 

 discharge, there being sometimes an absolute fall of temperature 

 in the latter case, when the C-R effect was allowed for. This is 

 partly due to the weakening and strengthening of the acid in the 

 solution, there being of course a corresponding absorption or pro- 

 duction of heat. Every one who has mixed acid and water is 

 aware of the latter fact. Again, on charging or discharging for 

 short periods, allowing the cell to stand idle for the same length of 

 time, it was observed that the temperature continued to rise after 

 the current had stopped. This was accounted for by supposing, 

 that, the distribution of current in the plugs not being uniform, 

 different parts of the same plug would be in different chemical 

 states, and local currents would be produced, tending to make the 

 plug uniform. These local currents cause losses, which exhibit 

 themselves finally as heat. The principal cause of loss, however, 

 seems to be due to the electrolysis of the solution, the loss from 

 this cause appearing as heat, and in the liberation of oxygen and 

 hydrogen from the two plates. The other losses are mainly due to 

 the formation of irreversible products in the form of lead salts. In 

 one discharge and charge cited, the total loss was 98 watt hours. 

 Of these, 51 watts were accounted for in heat ; the remainder must 

 have been due to irreversible chemical actions. The heat losses 

 may be classed as (i) the Joule effect, measured by CR ; (2) heat, 

 ing due to eddy-currents ; (3) heating due to electrolysis of the 

 solution into free hydrogen and oxygen. It should be noted that 

 the alternate heating and cooling due to the strengthening and 

 weakening of the acid is reversible, and therefore does not appear 

 as a loss. Of the losses due to chemical actions during charge, 

 which are not reversed on discharge, the most important, as far as 

 loss of energy goes, is the electrolysis of the solution into free 

 hydrogen and oxygen. The most important, so far as deteriora- 

 tion goes, is the formation of salts of lead on discharge in the weak 

 acid in the plug, from the material of the support-plate. This last 

 effect is exaggerated by rapid discharge, or by discharging until 

 the formation of the more bulky sulphate of lead has greatly de- 

 creased the diffusion. 



HEALTH MATTERS. 

 Women's Breathing. — Our readers will doubtless remember 

 the claim made by Dr. Thomas J. Mays of Philadelphia, that he 

 had succeeded in demonstrating that the statement made in almost 

 every text-book on physiology, that it was natural for women to 

 breathe from the chest, was wrong ; that the abdominal type of res- 

 piration, as ordinarily observed in men, was the natural type of 

 women as well, and the costal type as seen in women is the result 

 of modern dress. This claim he supported by the result of an ex- 

 amination of eighty-two American Indian girls. Dr. J. H. Kellogg, 

 from an examination of Chinese and other women untrammelled by 

 tight-fitting dress, finds the abdominal type present in them. Other 

 observers, notably Hutchinson, in twenty-four girls whose waists 

 had never been constricted by corsets or other appliances, found 

 the costal type present. The question of what is the natural type 

 of respiration may therefore still be regarded as sub judzce, unless, 

 which perhaps may be the truth, both types are natural under 

 varying conditions, independent of dress. 



