In those chapels prayer alone is in force, and Mary answers it without the help of any waters.

Indeed, She effects more moral than physical cures.

Notre Dame de Fourvieres at Lyon, Notre Dame de Sous-Terre at Chartres, Notre Dame des Victoires at Paris, to mention only three.
"Wherefore this difference?
None can understand, and probably none will ever know.

At most may we suppose that in compassion for the everlasting craving of our hapless souls wearied with prayer without sight, She would fain confirm our faith and help to gather in the flock by showing Herself.
"In all this obscurity," Durtal went on, "is it at least possible to discern some dim landmarks, some vague law?
"As we gaze into the darkness, two spots of light appear," he replied to himself.
"In the first place, this: She appears to none but the poor and humble; She addresses the simple souls who have in a way handed down the primitive occupation, the biblical function of the Patriarchs; She unveils herself to the children of the soil, to the shepherds, to girls as they watch the flock.

Both at La Salette and at Lourdes She chose little pastors for Her confidants, and this is intelligible, since, by acting thus, she confirms the known will of Her Son; the first to behold the infant Jesus in the manger at Bethlehem were in fact shepherds, and it was from among men of the lowest class that Christ chose His apostles.
"And is not the water that serves as a medium of cure prefigured in the Sacred Books--in the Old Testament by the River Jordan, which cleansed Naaman of his leprosy; and in the New by the probationary pool stirred by an angel?
"Another law seems no less probable.