LETTER LXVI. _Bureau des Longitudes_--Is on a more extensive scale than the Board of Longitude in England--National Observatory--Subterraneous quarries that have furnished the stone with which most of the houses in Paris are constructed--Measures taken to prevent the buildings in Paris from being swallowed up in these extensive labyrinths--Present state of the Observatory--_Lalande_, _Méchain_, and _Bouvard_--_Carroché_, and _Lenoir_--_Lavoisier_, and _Borda_--_Delambre_, _Laplace_, _Burckhardt_, _Vidal_, _Biot_, and _Puisson_--New French weights and measures--Concise account of the operations employed in measuring an arc of the terrestrial meridian--Table of the new French measures and weights--Their correspondence with the old, and also with those of England. LETTER LXVII. _Dépôt de la Marine_--An establishment much wanted in England. LETTER LXVIII. _Théâtre Louvois_--_Picard_, the manager of this theatre, is the _Molière_ of his company--_La Grande Ville, ou les Provinciaux à Paris_--Principal performers at this theatre--_Picard_, _Devigny_, _Dorsan_, and _Clozel_--Mesdemoiselles _Adeline_, _Molière_, _Lescot_, and Madame _Molé_--_Théâtre du Vaudeville_--Authors who write for this theatre--Principal performers--Public malignity, the main support of this theatre. LETTER LXIX. _Hôtel de la Monnaie_--Description of this building--_Musée des Mines_--Formed by M. _Sage_--The arrangement of this cabinet is excellent--_Cabinet du Conseil des Mines_--Principal mineral substances discovered in France since the revolution. LETTER LXX. _Théâtre Montansier_--Principal performers--_Ambigu Comique_--The curiosity of a stranger may be satisfied in a single visit to each of the minor theatres in Paris. LETTER LXXI. Police of Paris--Historical sketch of it--Its perfections and imperfections--Anecdote of a minister of police--_Mouchards_ --Anecdote which shews the detestation in which they are held--The Parisian police extends to foreign countries--This truth exemplified by two remarkable facts--No _habeas corpus_ in France. LETTER LXXII. The _savans_ saved France, when their country was invaded --Astonishing exertions made by the French on that occasion--Anecdote relating to _Robespierre_--Extraordinary resources created by the men of science--Means employed for increasing the manufacture of powder, cannon, and muskets--The produce of these new manufactories contrasted with that of the old ones--Territorial acquisitions of the French--The Carnival revived in Paris. LETTER LXXIII. Public gaming-houses--_Académies de jeu_, which existed in Paris before the revolution--Gaming-houses licensed by the police--The privilege of granting those licences is farmed by a private individual--Description of the _Maisons de jeu_--Anecdote of an old professed gambler--Gaming prevails in all the principal towns of France--The excuse of the old government for promoting gaming, is reproduced at the present day.