putting 



C Y A 



Brought forward 



533 



C Y A 



Drugs 



Grain 



Iron. 



Steel 



Japan wood 



Tutenague 



Tin 



Spices 



Sundries 



Treasure 



Sicca Rupees. 

 1,143,072 

 47,431 

 54,143 

 24,302 

 23,518 

 11,554 

 16,636 

 19,365 

 15,914 

 81,640 

 250,370 



Total amount of imports from India in sicca") , ^ g _ „._ 



rupees ..... J ' ' 



See Guzerat and Scindy. (j) 



CUTTING Engine. See Horology. 



CUXHAVEN. See Hamburg. 



CYAMUS. See Nehimbhun, Botany, p. 239. 



CYANEAN Isles. See Black Sea. 



CYANELLA, a genus of plants of the class Hexan- 

 dria, and order Monogynia. See Botany, p. 189 



CYANOMETER, from ku«i/»j, blue, and /mr^y, a 

 measure, is the name of an instrument, or rather of a 

 method invented by M. de Saussure for estimating the 

 intensity of the blue colour of the sky. A circular 

 band, or zone, made of thick paper or pasteboard, is 

 divided into fifty-one parts, each of which is painted 

 with a different shade of blue, varying by gradual tints 

 from the deepest blue, formed by a mixture of black, 

 to the lightest, which is formed by a mixture of white. 

 This coloured zone is then held in the hand of the obser- 

 ver, who notices the particular tint which corresponds to 

 the colour of the sky. The number of this tint, reckon- 

 ed from the greatest, will mark the intensity of the 

 blue colour of the sky at the time of observation. 



This instrument has been used not only by Saussure, 

 but also by the celebrated traveller Baron Humboldt, 

 and by M. Depons, to whom we are indebted for the 

 three following results : 



General intensity of the blue colour of the sky in 

 Europe ...... 14° 



Europe 

 Do. do. at Caraccas 

 Do. do. at Cumana 



18 



24 



Various opinions have been entertained respecting 

 the cause of the blue colour of the sky. Fromondus at- 

 tributed it to a mixture of light with the black space 

 beyond our atmosphere. Faber supposes it to arise 

 from the reflexion of the light by particles floating in 

 the ah - . Funccius, who wrote a treatise on the subject, 

 asserted, that the blue colour was a mixture of much 

 shade and little light. Otto Guericke maintained, that 

 white and black, when mixed together, will form a 

 blue like that of the sky ; and the same vague notion 

 received the support even of Wolfius and Muschen- 

 broek. Dr Eberhard imagines, that the air has a pro- 

 per colour of its own, in consequence of refracting the 

 blue rays more than others. It was reserved, however, 

 for M Bouguer to assign the most probable reason for 

 the blueness of the sky. The red rays being less re- 

 frangible than the blue ones, and less apt to be obstruct- 

 ed or thrown back in their progress through an imper- 

 fectly transparent medium, will consequently force their 

 way tlirough the atmosphere, while the blue rays, ha- 

 ving less power to overcome the resistance to which 

 they are exposed, will be reflected, and, of course, give 

 the sky a blue colour. 



This opinion, however, though rendered probable by 



many considerations, still required the evidence of de- Cyanome* 

 monstration, which we think it has lately received. te r - 

 " We have already seen." says Dr Brewster in his Trta- ""~~^ 

 Use on N'w Philosophical Instruments, p. 349, " that 

 the singular decomposition of light produced by the 

 intervention of a plate of mica, is exhibited only where 

 the transmitted rays have been previously polarised. 

 This alternation of the prismatic colours, therefore, may 

 be assumed as a decisive test, that the light by which 

 they are formed has received, either wholly or partly, 

 the character of polarisation ; and by thus distinguish- 

 ing reflected from direct light, it enables us to account 

 for several interesting phenomena which have been only 

 hypothetically explained. 



" When we examine the light of the clouds by a 

 prism of Iceland spar, and interpose a ptate of mica, 

 the alternation of the prismatic colours is distinctly vi- 

 sible, although none of the two images formed by the 

 spar vanishes in every quadrant It follows, therefore, 

 that the light of the clouds has been partly polarised by 

 reflexion 



" When the blue light of the sky is examined in a 

 similar manner, the play of the prismatic colours is still 

 more brilliant than in the preceding experiment, and 

 one of the images suffers a visible diminution of bright, 

 ness at every quarter of a revolution. Hence we may 

 conclude, that the blue light of the ski/ has experienced 

 a partial polarisation, and that it is reflected from the at- 

 mosphere with which the earth is surrounded!' 



M. de Saussure found, that the intensity of the blue 

 colour increased with the elevation above the level of 

 the sea ; and it has also been observed, that the inten- 

 sity of colour is diminished as the quantity of aqueous- 

 vapour is increased. Hence the measures taken with 

 the cyanometer are supposed to indicate the quantity 

 of water actually dissolved in the air. 



Another cyanometer, obviously more accurate than N*>w cya* 

 that of Saussure' s, and more deserving of the name of nometer, 

 an instrument, has been constructed by the writer of 

 this article. It consists of two plates of glass, about 

 twelve inches long, joined together at one end, so that 

 their surfaces may form an angle of from 12° to 20°. 

 These plates form two of the sides of a prismatic ves- 

 sel, which is filled with a blue fluid, having such an 

 intensity, that the blue colour near the top of the ves- 

 sel, where the distance of the plates is small, is less 

 than the minimum blue of the sky, while the intensity 

 of the blue colour at the bottom of the vessel exceeds 

 the deepest tinge which is ever found in the atmo- 

 sphere. Between these two extremes there is a regu- 

 lar gradation of tints, and by a proper adjustment of 

 the length of the plates to the angle which they form, 

 and to the intensity of the blue fluid, a scale of conve- 

 nient magnitude may be obtained. In using this in- 

 strument, a white circular spot may be made to move 

 upon a black ground, so as to be seen through the 

 fluid in any part of its progress from the one end to 

 the other of the prismatic vessel. The light which il- 

 luminates the white circular space, may be either couir 

 mon light, or, by making the white spot move in con- 

 tact with one of the glass plates, the light will first- 

 pass through the fluid to the white spot, and then be 

 reflected back again to the eye. In this last case, the. 

 intensity of the blue colour will be very great. 



By using four, six, eight, ten, or twelve glass plates, 

 a prismatic vessel with several sides may be construct- 

 ed ; and by making the distance of each pair of plates 

 different, and altering the angle which they form, a 

 scale of any magnitude may readily be obtained, (o) 



