What did the Cassells do with all the gas works tar which they bought? They were general tar distillers, selling tar products and fractions to whoever wanted them. A good example of their reputation was given in a patent case where the type of 'coal oil' was crucial. The chemist, Richard Phillips, acted as a consultant in this case and was asked by the judge where he had obtained his samples of tar used for the demonstration in court. He replied 'from Cassell at Millwall'. Similarly Thomas Hancock, who was to develop the emulsification of rubber using tar oils, went to Cassell to buy the selection of fractions needed for experiment. These cases suggest that Cassell were well known as tar distillers and had a reputation for quality.
What they produced and sold to customers was a variety of specialist distillates, which were called by the names used by the British Tar Company, Accum and the early Chartered promoters. Elsewhere chemists were working on a more sophisticated codification and analysis of coal based oil fractions. Sadly, there is simply not enough information about Cassell and tar distillers like him to know how far they were involved with such chemists and how much they contributed to their work.
PATENT LAVA STONE
A possible connection of Cassell with F.D. Morgan and Roman cement has been mentioned above. John Henry Cassell 's site at northern Millwall was called the 'Patent Lava Stone Works'. He seems to have developed a type of bituminous material there. He carried out a number of contracts using this material, including the paving of Vauxhall Bridge Road, in front of the Horns Tavern in Kennington and the flooring of Giblett's slaughterhouses in Bayswater. As a demonstration piece he paved the part of West Ferry Road behind his works. The material, which had all sorts of uses, seems in some ways to have provided an extension for his drainpipe business. He even used one of his mixtures for coffins in the crypt of the Brunswick Chapel, in Three Colt Lane. In 1837 he used it to cap the river wall in Greenwich for the Greenwich Commission of Sewers.
'Lava stone' is not obviously made with coal tar and Cassell 's publicity for it implies that it was made from natural bitumen. However, in view of the amount of coal tar he was buying its true ingredients must be open to question. Cassell was one of several manufacturers of artificial stone at the time that had strong links with gas works tar and the subject will be discussed again later.