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Stothert, Slaughter and Co of Avon Street, Bristol.
1840 An early order was for two broad gauge 7 ft 0¼ in (2140 mm) 2-2-2 Firefly class express passenger engines Arrow and Dart with 7 ft driving wheels delivered for the opening of the Great Western Railway from Bristol to Bath on August 31, 1840. This was soon followed by an order for eight smaller 2-2-2 Sun class engines with 6 ft drivers.
1842 Made two stationary engines to drive machinery at the GWR's works 
1843 Mention as the manufacturer of the Avon steamer driven by a screw 
1844 The works were renamed Avonside Ironworks. A shipbuilding yard was acquired at Hotwells and many ships were produced there.
1846 Built 'Avalanche' the first of five six-coupled saddle tank banking engines for the Great Western Railway.
1846 'Boiler Explosion at Bristol.- On Saturday morning steam-engine boiler exploded at the factory of Stothert, Hayter, and Co. [Hayter should presumably have been Slaughter], civil engineers, St. Philip's, Bristol, by which two men were killed, and several others were seriously injured. The workpeople were out at breakfast, except those belonging to the engine-house, and two men who had gone thither (contrary to rule) to take their morning repast. The explosion blew away the brickwork around the fire-boxes, scattering the boiling water and steam in all directions. Escape was impossible, and all present were covered with the scalding fluid, and received the most serious injuries. One poor young man, named John Thatcher, was scalded from head to foot, and that not only externally, but the boiling water and steam forced their way into his lungs and injured the air tubes. In the case of one of the deceased, the coroner's jury returned a verdict of accidental death.. See also below.
1846 'EXPLOSION OF A STEAM BOILER — THREE LIVES LOST. .... we proceed now to record the details of the disastrous event. It happened on Saturday morning, about quarter to nine o'clock, at the foundry of Messrs. Slothert, Slaughter, and Company, the extensive machine and engine manufacturers in Cheese-lane, St. Philip’s. At that hour five of the workmen, namely, Thomas Thatcher, apprentice, Joseph Walker, Francis Spicer, - Slade, and Thomas Crates, were in the engine-room, all sitting either on or near to the boiler, eating their breakfasts. On a sudden a powerful issue of boiling water and steam poured from the boiler, enveloping the whole of the unhappy men, scalding their persons externally in a most dreadful manner, and working yet more agonizing torture by the steam forcing its way down their throats. They were all immediately taken to the Infirmary. The boy Thatcher died before he reached the institution, Walker expired on Saturday night, and Spicer breathed his last on Monday morning. Neither of these were married. The two survivors, Slade and Crates, still lie in a dreadful and precarious state, but hopes are entertained of their recovery. Both of these are married men. Slade has no children, but Crates has three dependent on him.
The first inquest was held on Saturday afternoon, at the Infirmary, before J. B. Grindon, Esq., and a respectable jury, on the body of Thatcher. .... The Jury then, without hesitation, returned a verdict of Accidental Death. The inquest on the body of Joseph Walker, who died on Saturday night, was held at the Infirmary, on Monday, at three o'clock. ..... Verdict, Accidental Death. Francis Spicer, the third man, died on Tuesday morning, and the inquest was held the same day at three. ...
.... Some of the Jury expressed themselves dissatisfied that a more perfect examination of the boiler had not been made since the accident, it was now cold and parties could go inside it. To this it was replied by Mr. Washrough, cashier in the company, that Messrs. Stothert, Slaughter, and Co. had offered, if the Coroner thought it necessary, to take the boiler out and submit it to examination, but that gentleman had not deemed it requisite. The Coroner, on this, observed that his reasons for so doing were, that it would take a long time to get the boiler out, two days at the least,— that all parties were naturally anxious for a termination of the proceedings; that he did not anticipate any good result from the examination, seeing that they had the evidence of experienced persons that the boiler was considered a safe one [!] ; at the same time if the Jury wished it, he was willing to adjourn, and then they might examine the boiler themselves. He (the Coroner) had no authority to employ a party to examine the boiler, and no funds out of which to pay him.
A Juryman remarked that rumours were about, that Messrs. Stothert and Slaughter had been warned before that the boiler was not safe.
The Coroner said it was strange such parties had not come to him and had not appeared at the inquest. It was well known was always ready to sift every case to the bottom.
Mr. Wasbrough emphatically denied that any of the men had ever expressed any fear of the boiler.
After some further conversation, the Jury delivered and returned a like verdict to the other cases.' 
1849 Another large order came for ten broad gauge passenger 2-2-2's with 7 ft 6 in drivers and eight goods engines from the Bristol and Exeter Railway for the independent operation of that line from May 1, 1849.
1850 "NOTICE is hereby given, that the Partnership hitherto subsisting between us the undersigned, Henry Stothert, John Stothert, Edward Slaughter, George Fuller, and Robert Bruce, of the Avonside Iron Works, in the city of Bristol, Locomotive Engine Manufacturers, Ironfounders, and Makers of Machinery, carrying on business under the firm of Stothert, Slaughter, and Company, was this day dissolved by mutual consent, so far as the said Robert Bruce is concerned, who retires therefrom." — Dated this 5th day of August 1850.
1851 Award at the 1851 Great Exhibition. See details at 1851 Great Exhibition: Reports of the Juries: Class V.
1851 the company acquired a ship building yard, previously occupied by Lunell and Co, of which Henry Stothert took charge as a separate undertaking. Another branch of the family also had a shipbuilding business - See G. K. Stothert and Co
1852 Listed as Ironfounders in Bristol as Stothert, Slaughter and Co, Avonside ironworks, St. Phillips 
1856 The company became Slaughter, Gruning and Company when Henry Gruning joined the business; Stothert concentrated on the shipbuilding. By this time they had produced around 340 railway locomotives.
1860 Partnership change '...the Partnership hitherto subsisting between us the undersigned, Edward Slaughter, Henry Stothert, John Stothert, John Stephens, Henry Gruning, and Robert Stephen Cuthbertson, of the Avonside Iron Works, in the city of Bristol, Locomotive Engine Manufacturers, Ironfounders, and Makers of Machinery, carrying on business under the firm of Slaughter, Gruning, and Company, was this day dissolved, as on and from the 31st day of December last, by mutual consent, so far as the said Robert Stephen Cuthbertson is concerned, who retires therefrom....'
1861 The company was employing 680 men and 98 boys 
1864-6 Four engines for London Main Drainage (Deptford Station)
1864 With Edward Slaughter still in control, the company became the Avonside Engine Co. Mr. Slaughter retained the engineering and general management, taking the title of Managing Director, which post he held until 1873, when failing health induced him to abandon active work.