436 METEOROLOGY. 



band, which v/as reproduced by Kiirntz iu 1840, and by Schiibler* in 

 his four splendid engraved plates in 1849. In fine, the jjlates which 

 were i)j,iblished by the Smithsonian Institution t at Washington, and 

 in 1859 by tbe chart department of the French minister of marine,! 

 to serve as instructions for seamen and observers, were reproductions 

 of those of Kiirntz. The French edition alone contained two plates, 

 of which the first embraced the simple forms of clouds, cirrus, stratus, 

 cumulus, and nimbus, and the second the compound forms, cirro-cumu- 

 lus, cirro-stratus, and cum ulo- stratus, with four variable cirri. Howard's 

 Plate VI, on the contrary", published in 1803 for the first time, in Tilloch's 

 Philosophical Magazine, represents the stratus as a, mist spreading above 

 a lake surrounded by hills. Thus far in relation to the erroneous inter- 

 pretation given to Howard's stratus. We now proceed to note another 

 error hitherto propagated, relative to the nimbus. In the first place, 

 Kamtz's definition, which all the late meteorologists have adopted, is 

 as follows : When the cumulus is piled up and becomes more dense it 

 passes to the state cumulo-stratus, which often takes at the horizon a 

 black or bluish tint and passes to the state of nimbus, or rain-cloud. 

 This is distinguished by its uniform gray tint and its broken edges, the 

 clouds which compose it being so much confounded that it is impossible 

 to distinguish them. Thus the single primordial and distinctive char- 

 acter which results from this definition is that of a rain-cloud, and there- 

 fore we shall call every rain-cloud nimbus, as has been done to the present 

 time. Its secondary characteristics are : 1st, a tint of uniform gray ', 

 2d, its edges broken ; 3d, confusion of all the clouds of which it is com- 

 posed. All this gives no idea of the most essential element, namely, 

 the real form of the rain-cloud. Though the definition of Kiirntz, and 

 other writers, is not that of Howard, this observer has not given one 

 more intelligible and exact. We see that he unconsciously felt the 

 formation of rain-cloud, but was not very settled in his description. I 

 am speaking of the double suj)erj)osed stratum, the inferior formed of 

 cumulus, which it designates, and the second superior stratum of cirrus, 

 whose existence was vaguely felt by Howard. The remainder of his 

 definition is cumulus cirro-stratus vcl nimhus def. nubes vel ombium con- 

 fjerieo fsupernc cirrata) pluvian cffundens. A cloud or system of clouds 

 from which rain is falling is called a rain-cloud. It is a horizontal sheet, 

 above which the cirrus spreads, while the cumulus enters in laterally 

 and from beneath. In other isolated passages of his long description 

 of the nimbus, the idea of this double stratum appears yet more plainly. 

 " Clouds, in any one of the preceding modifications, may increase so as 

 completely to obscure the sky. Before this eifect takes place there ex- 

 ists, at a greater altitude, a thin, light veil, or at least a hazy turbidness. 



* ScHUBLER. — Grundsiitze der Metsorologie, Leipzig, 1849. 

 t Smithsokian Institution, Washiugton, D. C. 



X ViVXEECHOUT. — Freucli translatiou of tlio " Explauatious aud Sailing Directions of 

 Lieutenant Maury," Paris, 1S59, 4to. 



