The great desideratum in a seat on horseback is that it should be firm.
Primum et ultimum hoc in botanicis desideratum est.
Delaunay, developed in his Theorie du mouvement de la lune (2 vols., 1860, 1867), because it contains a germ which may yet develop into the great desideratum of a general method in celestial mechanics.
It remained a desideratum to express by equations the motion of a particle of the fluid in any assigned direction.
He now fixed his residence at Islington, engaged chiefly upon lunar observations, with a view to the great desideratum of a method of finding the longitude at sea.