1835.] Accidental and Complementary Colours. 295 



1 . Let two semi-circles of coloured paper, a red and a 

 green, for instance, be pasted upon one surface of a disk of 

 pasteboard, of about five inches in diameter, and by com- 

 municating a rapid rotating motion to the disk,* the result 

 will be white, by the combination of the two tints from direct 

 impression. 



2. Between the green disk and the plane reflector of the 

 perichromascope, place a portion of sesqui-oxide of lead, 

 the green disk being really complementary to the colour of 

 powder, and the red powder will appear black, as black as 

 lamp-black ; the combination of the two tints being effected 

 by superposition. 



(To be continued.) 

 Salisbury, Sth September 1835. 



Article VII. 



On Mali. By Robert D. Thomson, M.D. 

 C Continued from vol. i. p. 449 .J 



I. The first step of the process consists in placing the malt 

 in the steep, a square chamber, which is lined with stone and 

 lime, and is usually sunk below the level of the barn floor, 

 having been previously filled to the proper height with 

 water .f The malt is allowed to remain here for not less 

 than 40 hours, by legal regulations. The light seeds which 

 swim on the surface are skimmed off, and the mass of grain 

 is levelled, for the purpose of being gauged. The time 

 during which the malt is allowed to remain in the steep 

 varies, according to the will of the malster. But the usual 

 test of its fitness for being removed is the capability of its 

 extremities being squeezed together between the fingers. 



* The accidental iintsofihese fundamental colours may be revived during rapid 

 rotation. I have considered this, and analogous facts, sufficiently important to 

 devote a paper to the subject, especially as the fact is easily explained on existing 

 principles. This paper will appear shortly. 



t Professor Lavini finds the composition of wheat as follows: 1. Ripe com 

 contains 75 per cent, of starch ; unripfe com only 60 per cent. 2. Unripe com 

 contains ^ of its weight of mucous extractive matter. 3. In unripe com there is 

 about -g^Qth of gluten ; in ripe com 25 per cent. 4. The albumen is the same in 

 both. 5. In unripe corn there is a green resin, amounting to about ^^^th, which 

 is probably converted into gluten and gum as vegetation advances. 6. Both contain 

 oxides of copper, iron, and manganese. — Meniorie della Realc Accadem dele Scien. 

 di Torino, xxxvii. 



