Verses 2&3 are listing numerous items (mostly architectural) which might be sold. Doyle would seem to be suggesting that as well as the specific instances there are 50 other temples which might be sold as well. I don't know if Doyle had a particular 50 temples in mind, but it might be relevant that St Clement Danes is one of the works of Sir Christopher Wren, who was instrumental in the building/rebuilding of many fine churches after the great fire of London.

His choice of an archaic word fits the verse, though whether it was as archaic in Doyle's time I don't know. There will always be those who rejoice in sending their readers scuttling for a dictionary. Whether they do it out of intellectual snobbery, or simple joy in finding the precise word for their purpose, is for the reader to judge. Either way it can be an annoying trait for the reader to handle, or an educational one, it depends on the reader.