From Dr Archibald Billing   4 February 1854

My dear Sir

I shall be delighted to see you any day you happen to be in town and I never leave home before 12 o-clock—

I am not surprised that you did not quite understand my statement about the bort and carbonate— for it is difficult to disentangle the scientific from the trade terms whenever we begin to speak of specimens which enter into jewellery—

Bort is an old name given in trade to those diamonds which not being good enough to form into brilliants are grounded into diamond dust for the purpose of skitting and grinding the surface of various diamonds & rubies sapphires agates &c—

You have set down bort in the table as synonymous with carbonate, but the latter is a new discovery and though beginning to be substituted in some works for bort is inferior in hardness, price &c the bort being recognized as real diamond, the carbonate not yet by the tradesmen though I doubt not it will be proved so by mineralogists.

If you have the least wish I will send you a few more bits of bort dust when I last wrote I had no more by me. I wish you success in your laudable endeavors and remain

Yours most truly | Dr Billing