Paris as It Was and as It Is / A Sketch Of The French Capital, Illustrative Of The Effects Of The Revolution

by Francis William Blagdon

The subterraneous vaults have served for meteorological experiments. In one of them water is seen to petrify on filtering through the rock above. They lead to near fifty streets or passages, formed by quarries excavated in procuring the stones with which great part of the city of Paris is constructed.

Previously to the year 1777, churches, palaces, whole streets of houses, and the public highway of several quarters of Paris and its environs, were on the point of being swallowed up in gulfs no less vast in depth than in extent. Since then, considerable works have been undertaken to consolidate these subterraneous caverns, and fill up the void, equally dangerous, occasioned by the working of the plaster-quarries.

An accident of a very alarming nature, which happened in the Rue d'Enfer in the year 1774; and another, at Montmenil, in 1778, shewed the necessity of expediting these operations, which were followed up with great activity from 1777 to 1789, when their progress was relaxed from the circumstances of the times. These quarries are far more extensive than is commonly imagined. In the department of the Seine alone, they extend under all the south part of Paris, and the roads, plains, and communes, to the distance of several leagues round the circumference of this city. Their roof, with the edifices standing on the soil that covers it, is either supported by walls recently built under the foundation of those edifices, or by pillars constructed at different periods in several places. The government is at the expense of providing for the safety of the streets, highways, and public buildings, but that of propping under-ground all private habitations must be defrayed by the proprietor. These ancient quarries had been much neglected, and the means of visiting them was equally dangerous and inconvenient. At present, every precaution is taken to insure the safety of the persons employed in them, as well as the stability of their roof; and for the better superintendance of all the subterraneous constructions of Paris, galleries of communication have been formed of sufficient width to admit the free passage of materials necessary for keeping them in repair.

Let us now find our way out of these labyrinths, and reascending to the surface of the soil, pursue our examination of the Observatory.

In a large room on the first floor is traced the meridian line, which divides this building into two parts. Thence, being extended to the south and north, it crosses France from Colieure to Dunkirk.

On the pavement of one of the rooms is engraved a universal circular map, by CHAZELLES and SÉDILLAN. Another room is called the Salle aux secrets, because on applying the mouth to the groove of a pilaster, and whispering, a person placed at the opposite pilaster hears what is said, while those in the middle of the room, hear nothing. This phenomenon, the cause of which has been so often explained, must be common to all buildings constructed in this manner.

In speaking of the Champ de Mars, I mentioned that LALANDE obtained the construction of an Observatory at the ci-devant École Militaire. Since 1789, he and his nephew have discovered fifty thousand stars; an immense labour, the greater part of them being telescopic and invisible to the naked eye. Of this number, he has already classed thirty thousand.

The CASSINIS had neglected the Observatory in Paris; but when LALANDE was director of this establishment, he obtained from BONAPARTE good instruments of every description and of the largest dimensions. These have been executed by the first artists, who, with the greatest intelligence, have put in practice all the means of improvement which we owe to the fortunate discoveries of the eighteenth century. Of course, it is now as well provided as that of Greenwich. MÉCHAIN, the present director, and BOUVARD, his associate, are extremely assiduous in their astronomical labours.

CARROCHÉ has made for this Observatory a twenty-two feet telescope, which rivals those of HERSCHEL of the same length; and the use of reflecting circles, imagined by MAYER, and brought into use by BORDA, which LENOIR executes in a superior manner, and which we have not yet chosen to adopt in England, has introduced into the observations of the French an accuracy hitherto unknown. The meridian from Dunkirk to Barcelona, measured between the years 1792 and 1798, by DELAMBRE and MÉCHAIN, is of an astonishing exactness. It has brought to light the irregularity of the degrees, which was not suspected. The rules, composed of platina and copper, which LAVOISIER and BORDA imagined for measuring bases, without having occasion to calculate the effect of dilatation, are a singular invention, and greatly surpass what RAMSDEN made for the bases measured in England.

LAPLACE has discovered in the Moon inequalities with which we were not acquainted. The work he has published, under the title of Mécanique Céleste, contains the most astonishing discoveries of physical theory, the great inequality of Jupiter and Saturn, the acceleration of the Moon, the equation of the third Satellite of Jupiter, and the flux and reflux of the sea.