Before progressing too far, we must mention the early work of William Henry.  In 1804 he described publicly a method of producing coal-gas.  Besides making experiments on production and utilization of coal-gas for lighting, he devoted his knowledge of chemistry to the analysis of the gas.  He also made analytical studies of the relative value of wood, peat, oil, wax, and different kinds of coal for the distillation of gas.  His chemical analyses showed to a considerable extent the properties of carbureted hydrogen upon which illuminating value depended.  The results of his work were published in various English journals between 1805 and 1825 and they contributed much to the advancement of gas-lighting.

Although Clegg’s original gas-meter was complicated and cumbersome, it proved to be a useful device.  In fact, it appears to have been the most original and beneficial invention occasioned by early gas-lighting.  Later Samuel Crosley greatly improved it, with the result that it was introduced to a considerable extent; but by no means was it universally adopted.  Another improvement made by Clegg at this time was a device which maintained the pressure of gas approximately constant regardless of the pressure in the gasometer or tank.  Clegg retired from the service of the gas company in 1817 after a record of accomplishments which glorifies his name in the annals of gas-lighting.  Murdock is undoubtedly entitled to the distinction of having been the first person who applied gas-lighting to large private establishments, but Clegg overcame many difficulties and was the first to illuminate a whole town by this means.

In London in 1817 over 300,000 cubic feet of coal-gas was being manufactured daily, an amount sufficient to operate 76,500 Argand burners yielding 6 candle-power each.  Gas-lighting was now exciting great interest and was firmly established.  Westminster Bridge was lighted by gas in 1813, and the streets of Westminster during the following year.  Gas-lighting became popular in London by 1816 and in the course of the next few years it was adopted by the chief cities and towns in the United Kingdom and on the Continent.  It found its way into the houses rather slowly at first, owing to apprehension of the attendant dangers, to the lack of purification of the gas, and to the indifferent service.  It was not until the latter half of the nineteenth century that it was generally used in residences.

The gas-burner first employed by Murdock received the name “cockspur” from the shape of the flame.  This had an illuminating value equivalent to about one candle for each cubic foot of gas burned per hour.  The next step was to flatten the welded end of the gas-pipe and to bore a series of holes in a line.  From the shape of the flames this form of burner received the name “cockscomb.”  It was somewhat more efficient than the cockspur burner.  The next obvious step was to slit the end of the pipe by means of a fine saw.  From this slit the gas