High fashion on parade in Paris 1855

Loretta reports;

In the 19th century, Longchamps (also called Longchamp) was the place to see and be seen during Easter Week.  It was a combination Easter Parade/Paris Fashion Week.  The very latest modes were on parade—and the designs quickly copied by ambitious dressmakers all over the world.
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PARIS is a strange place, its inconsistencies are enough to bewilder all sober-minded people. Here, during the week preceding Easter a grand procession of carriages and well-dressed “folk" parade, up and down the Champs Elysées, displaying all the new inventions of the conclave of milliners, dress-makers, perfumers, shoemakers, embroiderers, etc., etc., and which all the rest of the world are to copy. The Parisians wander up and down this promenade, gayly, and with smiling faces, the vanities of this world being uppermost in their thoughts, never thinking that originally this procession was a pilgrimage, and instead of a worldly fête, a religious penance.

Yes, at the end of Champs Elysées, stood formerly the Convent of Longchamps— here holy nuns, with voices of unearthly beauty, cultivated by the greatest masters, sang the penitential psalms, and chaunted the solemn music of passion-week. The court of Louis XIV. took it into its head to go and join these harmonious nuns in their devotions, and say its prayers in the artistically arranged chapel, made to look like a beautiful representation of the Entombment. At first, every one went in sad colored dresses and, on Good Friday, actually submitted to a slight sprinkling of ashes, though they dispensed with the sack-cloth, but soon, very soon, this decorous behavior degenerated into a rivalry of pomp and show. Vanity came into play, as it always will where there is a large assembly of "fair women and 'brave men," and though they still went to hear the chaunting and to do penance, they proceeded to the convent in magnificent attire and splendid equipage. In Louts XV.'s time, Longchamps had thoroughly changed its aspect, and the gay procession was made more brilliant by notorious but sumptuous young ladies, who certainly never dreamed of entering a chapel. So at last, in after years, the time and place of the Longchamps procession remained the same, but the convent ceased to be frequented and the nuns to sing. Now, there is no longer any convent, and from what was a religious observance, has sprung the present promenade at which takes place the great change in the cut and color of mantle, dress and bonnet, and which are called Modes de Longchamps.

—Graham's American monthly magazine of literature, art, and fashion, 1855

The illustration, of 1830s fashion (because I couldn't put my hands on any 1850s Longchamp styles), is from French Fashion Plates of the Romantic Era, edited by Judy M. Johnson.