I haven't yet been able to get my hands on the 1844 article by Jules Dupuit
in "Annales des Ponts et Chauss?es, 6e cahier 1844". But I did find his
1849 follow-up article, repeating, discussing, and expanding his original
ideas: "De l'influence des peages sur l'utilite des voies de
communication", in: "Annales des Ponts et Chauss?es, nos. de mars et avril
1849".

It is on pp.308-390 in the 1877 collection - by the Library of the French
Department of Finance - of articles on the political economy of transport
and communications, entitled "Des voies de communication en France; recueil
de brochures".

You can download it - for free: a considerable utility at zero exchange
value! - at "gallica.bnf.fr", signature: BNF N0035549_PDF_1_448.pdf .

For your convenience, I have also extracted the 1849 article, cropped the
pages, and put it on top of the download section in my website at
www.condorcet.nl.

With kind regards,

Marcel Claessen