It is scarcely possible not to feel that the investigations here briefly sketched, possess unusual interest.  As Ehrenberg says, the subject is one ’of vast, manifold, and rapidly-increasing importance, and is but the beginning of a future great department of knowledge.’  Now that it has been published in a connected form, and the attention of scientific observers directed to it, we may hope soon to hear of corroborative evidence from all parts of the world.  We may mention, as bearing on the question, that sand-showers are not unfrequent in China.  Dr M’Gowan of Ningpo, in a communication to the Asiatic Society of Bengal, states, that at the beginning of 1851, three showers occurred within five weeks; the last, which commenced on the 26th March, and continued four days, being the heaviest.  The wind during the time varied from north-east to north-west, the breeze interrupted by occasional calms.  No rain had fallen for six weeks; and though, as the doctor observes, ’neither cloud, fog, nor mist obscured the heavens, yet the sun and moon were scarcely visible; the orb of day appeared as if viewed through a smoked glass, the whole sky presenting a uniform rusty hue.  At times, this sameness was disturbed, exhibiting between the spectator and the sun the appearance of a water-spout, owing to the gyratory motions of the impalpable mineral.  The sand penetrated the most secluded apartments; furniture wiped in the morning, would be so covered with it in the afternoon, that one could write on it legibly.  In the streets, it was annoying—­entering the eyes, nostrils, and mouth, and grating under the teeth.  My ophthalmic patients generally suffered a relapse, and an unusual number of new cases soon after presented themselves.  Were such heavy sand-storms of frequent occurrence, diseases of the visual organs would prevail to a destructive extent.’

These showers sometimes spread over several provinces at once, and far out to sea.  The Chinese call them yellow-sand.  Their source is the great desert of Gobi, or Sand-Ocean, more than 2000 miles long, and from 300 to 400 broad, in the interior of Asia.  Dr M’Gowan states, that the fall amounted to ten grains per square foot, but without specifying whether this quantity includes the whole duration of the shower.  During calms, it remains suspended.  The dust thus raised from the Mongolian steppes gives the peculiar tinge to the Yellow Sea.

Notwithstanding the annoyance of these dust-showers, they have a valuable compensation.  The Chinese, whose closeness of observation in agricultural matters is well known, assert that they are always followed by a fruitful season—­not, it is true, as cause, but as effect.  The explanation is, that the soil of the provinces most subject to the visitation, being of a compact character, is loosened and lightened by the sand borne on the wind from the Tatarian plains, and at the same time, the lighter fertilising matters carried away by the great rivers are replaced; and thus, that which at first sight appears an unmitigated evil, becomes the cause of good harvests, for they invariably follow a fall of sand.