Franklin

Another hand-written addition to Barbeu-Dubourg’s timeline, which adds credence to the idea that the additions were written by the original author himself, is in 1752, ‘orages demontrés electrique’ - storms shown to be electrical.

In 1750, Benjamin Franklin had published a proposal for an experiment to prove that lightning was electricity by flying a kite in a storm, and such an experiment had been carried out by others in 1752. Franklin and Barbeu-Dubourg became friends and corresponded frequently. The correspondence can be seen here. Barbeu-Dubourg translated many of Franklin’s works into French (Aldridge 1951).

Franklin was also a friend of the other pioneer of the arithmetic timeline, Joseph Priestley. In Barbeu-Dubourg’s very first letter  to Franklin, he acknowledges receiving a copy of Priestley’s own timeline, and tactfully emphasises his own priority in invention while assuring Franklin that he won’t make an issue of it:

J’ai reçu avec reconnoissance et vu avec plaisir la carte biographique de M. Priestley qui est effectivement construite presque sur les memes principes que la mienne, sans plagiat de part ni d’autre, car je ne pretens point me prevaloir de la date.

I have received with gratitude and viewed with pleasure the biographical chart of Mr. Priestley which is in truth made on almost the same principles as my own, without plagiarism on either side, as I in no way claim primacy on account of the date. 

References
Aldridge, Alfred Owen. 1951. Jacques Barbeu-Dubourg, a French disciple of Benjamin Franklin. Proceedings of the American Philosophical Society. 95(4). 331-392.