In reply to OP & French Erick:
Re spelling Chamonix
I have in front of me photocopies of the Réglements de la Compagnie des Guides de Chamonix. All use the spelling of today CHAMONIX
The first that of July 1821 Déliberation du Conseil de la Commune de Chamonix... written in manuscript signed Louis Simon Couttet. Ditto the second dated 9 May 1823, confirming the above by a Manifeste de la Royale Chambre des Comptes, printed Chambéry. Ditto various modifications; viz a model sent by the Sous-Préfecture de Bonneville for altering the text adopted unanimously by members in 1929 and in turn modified by a vote of. 85 out of 95, 22 March 1936 (in these we see -Mont Blanc is added to Chamonix)
The small painting presented by the Chamoniards to Napoleon III on his visit after the Referendum also spells it Chamonix
Spellings which omit the terminal x almost certainly arise from the fact that in Savoie the x is silent Cf Oyonax for example, as too a terminal z eg in the personal name of the photographer Tairraz.
Out of more general interest is to note that the )( >X was a medieval shorthand for ss. Eg Auxerre is pronounced Aussere and more importantly Bruxelles Brussels (as too in sprouts) a fact almost totally ignored by most commentators as well as the general public today, except the British!
Post edited at 13:03