The invention of the barometer and Torricelli's explanation of the vacuity above the mercury column placed before the members of the Florentine academy a ready method of obtaining vacua; for to exhaust a vessel it was only necessary to join, by means of a tube provided with stopcocks, the vessel to a barometer tube, fill the compound vessel with mercury and then to invert it in a basin containing this liquid, whereupon the mercury column fell, leaving a Torricellian vacuum in the vessel, which could be removed after shutting off the stop-cocks.
In both genera, as in the okapi, there is a vacuity in front of the orbit.
A preorbital vacuity of such dimensions as to exclude the lachrymal bone from articulation with the nasal.
In the skull the gland-pit is shallow, and the vacuity of moderate size; the nasal bones are well developed, and much expanded at the upper end.
Adherents of the Yoga philosophy and the system of ascetic practices enjoined by it with the view of mental abstraction and the supposed attainment of superhuman powers - practices which, when not merely pretended, but rigidly carried out, are only too apt to produce vacuity of mind and wild fits of frenzy.