April 24, J J 



SCIENCE, 



843 



importance, for the quantity of light emitted by a 

 glowing substance rises in a more rapid proportion 

 than the temperature of that substance. 



In 1838 we find Professor Jobard of Brussels say- 

 ing that " a small strip of carbon in a vacuum, used 

 as a conductor of a current of electricity, would emit 

 an intense, fixed, and durable light." De Changy, a 

 former pupil of Jobard, seems to have taken these 

 words as advice, for he commenced his experiments 

 in that line almost immediately afterwards. About 

 this time an Englishman named Moleyns also made 

 an incandescent lamp by using platinum. De- 

 Changy' s experiments failed because the strips of 

 gas-carbon which he used became disintegrated by the 

 current, and, as his globes were not perfectly ex- 

 hausted or sealed, the carbon gradually consumed 

 away. 



About the year 3843, J. W. Starr of Cincinnati 

 entered upon a thorough study of the light, and 

 found in Peabndy a munificent promoter of his plans. 

 After helping Starr in every way, Peabody sent him 

 to England to exhibit his invention. Before start- 

 ing on his voyage, Starr procured himself a compan- 

 ion named King, a shrewd man of business, who 

 immediately had a large chandelier constructed with 

 twenty-six electric glow-lamps, which were to sym- 

 bolize the states of the Union. The novel spectacle 

 was gazed upon by large crowds; and Faraday, after 

 witnessing the experiments, signified to his, American 

 brother electrician his great satisfaction with the 

 result. 



Starr died on the return voyage, and King patented 

 the lamp in his own name. This patent was granted 

 on the 4th of November, 1845, and refers to ' a glow- 

 ing carbon strip in a vacuum.' But with the death of 

 Starr the necessary funds ceased to flow, and in a 

 short time the promising glow-lamp was consigned to 

 oblivion. 



A very similar fate befell the inventions of the 

 Englishmen Greener and Staite, who patented, in 

 1846, another carbon-lamp. Starr formed the neces- 

 sary vacuum by using a tube thirty-six inches long, 

 filled with mercury; but the generation of electricity 

 was at that time far too expensive, although as re- 

 gards the clearness of the light, and the durability of 

 the carbon, the lamp was a success. 



In 1849 Petrie proposed to patent the use of iridi- 

 um, but the scarcity of that metal rendered it out of 

 the question. In 1855 DeCbangy resumed his stud- 

 ies with renewed zeal, occupying himself with the 

 construction of a lamp in which platinum formed 

 the conductor, and in 1858 patented a current reg- 

 ulator which enabled him to use his lamps for the 

 illumination of mines, submerged for fishing-pur- 

 poses, and in a nautical telegraph system by which 

 signals were displayed from the mast-heads of vessels. 

 The platinum was submitted to a preparing process 

 of separation, being maintained heated for some time 

 at a moderate degree of redness, and then gradually 

 raised to that degree of heat to which it would be 

 afterwards subjected in the lamp. 



At intervals of ten and fifteen years after the in- 

 ventions of Starr and of DeChangy, the incandescent 



lamp was revived, with partial success; but it was riot 

 until Edison and Swan put their shoulders to the 

 wheel that a perfect and practical lamp was con- 

 structed. 



In the year 1878 Edison was journeying in the 

 Rocky Mountains, when a companion awakened 

 within him the desire of occupying himself with 

 electric lighting, and on his return to Menlo Park he 

 furnished himself with the necessary apparatus. 

 Like DeChangy, he imagined that it would be easier 

 to use metal than carbon; and, with the abundant 

 funds furnished him by the Edison electric-lighting 

 company, he was enabled to reach almost every sub- 

 stance which his fertile brain might suggest. For 

 instance: it is said that his attention was called to 

 thorium, — a metal particularly difficult to fuse; and, 

 when a mineralogist informed him that there was not 

 a half-ounce of thorium in the whole territory of 

 the United States, Edison called up one of his assist- 

 ants, and, telling him that in one of the gold-mines 

 of the north-west a quantity of monarite crystals 

 (from which thorium is extracted) had been found, 

 gave him a letter of credit, with instructions to bring 

 him in the shortest possible time a hundred pounds 

 of monarite. In a few weeks Edison had the mona- 

 rite, and forthwith began his experiments. But 

 thorium also failed; and platinum was again tried, 

 this time with a certain amount of success. 



Meanwhile the dynamo-machine and the Sprengel 

 air-pump had been perfected. An Englishman named 

 J. W. Swan now obtained fair results with a filament 

 of charred cardboard, and found that the rapid con- 

 sumption and consequent breaking of the glowing 

 carbon was an almost insuperable impediment to his 

 success, and he also found that the inner walls of his 

 lamp became darkened by a deposit of some kind. 

 These troubles must have been of a most alarming 

 character. But Swan went on, and obtained the co- 

 operation of a Mr. Stearn, who was considered a great 

 authority as regards perfect vacuum. Evidently he 

 also fully understood that the carbon must be pre- 

 viously heated to whiteness in a good vacuum ; and 

 in 1877 he sent to Mr. Stearn a quantity of carbon- 

 ized cardboard strips, requesting that they be mounted 

 in glass bulbs, subsequently to be exhausted as per- 

 fectly as possible. This seems to have been done 

 with rare ability by raising the carbon to a very high 

 degree of heat by means of an electric current, which 

 set free the^gases it contained, and afterwards removed 

 them. The ends of the filaments were also made 

 thicker; and when the connections were made good, 

 and the vacuum sufficient, the glass bulb containing 

 the glowing carbon did not blacken, and the con- 

 sumption of the filament was infinitesimally small. 

 There only remained to make the lamp mechanically 

 perfect; and in 1878 Swan publicly exhibited his glow- 

 lamp, which possessed all the essential characteristics 

 of that in use at present. In the same year Edison 

 discarded metals, and followed in the footsteps of the 

 carbon men. Being forestalled by Swan, Mr. Edison 

 could not use cotton thread in his lamp, and, after a 

 lonqj series of experiments, decided upon the use of 

 filaments made out of a species of bamboo. 



