The correspondence series consists of letters written to Darby. The responses from Darby are not included, but in some cases, there are notes on the envelopes as to whether the letter has been answered. There is also a postcard featuring an illustration including a number of the founding members of the Brethren movement.
A selection of the correspondence relates to discussion of the divisions within the brethren, and interpretation of scripture, there is a letter written in French, and there are letters giving news of the work of Brethren assemblies in Britain.
A good proportion of the correspondence consists of letters from Robert T. Grant, relating to news of brethren assemblies in Canada and the United States of America.