600
HISTORY OF ENGINEERING.
Book T.
there is no time lost between the sending and the receipt of the intelligence. To conveythe wires from one station to another, posts 16 or 17 feet high are fixed in the ground atevery 400 or 500 yards, which support them in the air. Three wires on the lines, one ap-paratus and one set of wires at each station, are all that is required to complete themachine.
The battery at each station is about 2 feet in length, and 6 inches in width : if the wiresconnected with it were kept continually attached to the signal wires, they would produceconstant motion at the other end ; to obviate this another wire conducts the electricity intothe earth when the telegraph is not at work, and an attendant is always present at eaclidial; when a signal is made, he attaches the wire again to the battery. The wires are allcopper and coated with zinc.
Gas Lighting. — About the year 1739, there is a notice in the Philosophical Transactions of the discovery of coal-gas by the Rev. John Clayton, Dean of Kildare; this gas, called“ the spirit of coal,” was obtained from a retort placed in an open fire, and Dr. Claytonobserves, that “ at first there comes over only film, afterwards a black oil, and then aspirit arose which could not be condensed, and it broke the lute as well as the glasses.This spirit caught fire at the flame of a candle, and continued burning with violence as itissued out in a stream ; a quantity was collected in bladders, and a hole being made, thegas as it issued was lighted, and allowed to burn out for the amusement of his friends.”
In the year 1767, Dr. Richard Watson, afterwards Bishop of LlandafF, made some ex-periments upon the distillation of pit coal; he allowed the gas to mount by curved tubes,and describes, in the second volume of his chemical essays, its great inflammability as wellas elasticity ; he also found that it retained the former property after it had passed througha great quantity of water.
These discoveries do not appear to have been applied to the purpose of lighting untilsome years afterwards : in the streets of the metropolis, as well as those of most of the pro-vincial towns of importance, oil lamps were used, though very inadequate to their purpose,and it is difficult to say how or by whom coal gas was first introduced as an illuminator.
Mr. Murdoch, Mr. Southern, Mr. Clegg , and Mr. Henry Creighton, all resided at Soho,near Birmingham , at the same time; and without doubt Mr. Murdoch used coal-gas for thepurpose of lighting his house and offices at Redruth in Cornwall in the year 1792, and fouror five years afterwards he introduced the system into Scotland . Jn the year 1798 he con-structed an apparatus upon an extensive scale at the great manufactory of Bolton and Watt,near Birmingham , where the first attempts were made to purify the gas ; and at the peace of1802, the manufactory at Soho was illuminated by it with a variety of devices on theexterior, to the astonishment of all who beheld it.
Various manufactories were afterwards lighted with coal-gas, but it was not used in thestreets till the year 1807, when a portion of Pall Mall in London was illuminated by Mr.Winsor, who proposed the establishment of a national light and heat company. The retortused on this occasion to distil the coal was an iron vessel, with a cover well-fitted and lutedto the top ; in the centre of the lid was a pipe, which conveyed the gas to a condensingvessel of a conical form ; this was divided into two or three separate compartments by platesbored with a number of holes, so that the gas might spread, and more readily purify' itself'from the sulphuretted hydrogen and ammonia, which it did, though very imperfectly. Thepipes laid down as mains were lead, with copper burners to the branch pipes, which wereargands, jets, and batswing, as in present use.
Dr. William Henry gave a series of lectures at Manchester in the y*ear 1804, and duringthe course he exhibited the mode of producing gas from coal, and its use as a material foryielding light. Mr. Samuel Clegg at this time, having left Soho, began to direct his atten-tion to the construction of gas-light apparatus, and one of his first works was lighting acotton-mill near Halifax in Yorkshire . Hie subject was soon afterwards taken up by Mr.Josiah Pemberton, of Birmingham . His apparatus consisted of a cast-iron vessel, like acottage pot, and would contain from 15 to 30 pounds weight of coal ; a strong cover witha pipe fitted on carried the gas to the purifying cistern, ascending and descending in itspassage through the water ; it was thus well condensed and washed before it entered thegasometer, which was suspended by a weight over a large wooden vat. The pipes thatcarried the gas were made of tinned iron or copper.
In the year 1809, an application was made to parliament for the establishment of thepresent London and Westminster Chartered Gas Light and Coke Company: this was opposedby Mr. Murdoch, on the ground of his having a priority of right to the discovery, but it waseventually embodied by legal authority, and having a large capital at command, the worksfor lighting the streets were commenced ; but the subscribers becoming dissatisfied with theproceedings, a change of management took place, and in 1812 a charter was grantedfor the term of twenty-one years. The following year, by the assistance of Mr. SamuelClegg , great improvements were introduced throughout all the operations, and to him weare indebted for the horizontal rotative retort for purifying coal-gas with cream of lime,for the rotative gas-meters, and for the self-acting governor: he also greatly improved the