He became an honorary member of the Institute of Actuaries, and his contributions to the ‘Journal’ of that society were numerous and valuable.
He undertook, purely as a labour of love, the task of organising and preparing for publication the tables deduced from the mortality experience issued by the institute.
Gray specially constructed for Part I. of the ‘Institute Text Book’ an extensive table of values of log 10 (1 + i), appending thereto an interesting note on the calculations.
With Henry Ambrose Smith and William Orchard, Gray published ‘Assurance and Annuity Tables, according to the Carlisle Rate of Mortality, at three per cent.,’ 8vo, London, 1851, and contributed a preliminary notice to William Orchard's ‘Single and Annual Assurance Premiums for every value of Annuity,’ 8vo, London, 1856.
‘Tables and Formulæ for the Computation of Life Contingencies; with copious Examples of Annuity, Assurance, and Friendly Society Calculations,’ 8vo, London, 1849.