70 Royal Institution of Great Britain. 



to one part of the rope half way between the anchor and the shore} 

 this buoy carries a loop, and through that loop the other part of the 

 rope passes. A boat made fast to one end of this rope is easily 

 hauled through the surf, and can then proceed to give assistance to a 

 ship in distress. 



June 4.— Mr. Brockedon on the perception and application of co- 

 lour. Mr. Brockedon's observations related to the manner in which 

 the eye perceived colours, with their agreement and disagreement, 

 and to some of the compensating forces appointed by nature to pre- 

 vent distress to that organ when under the influence of bright colours. 

 After remarks upon the complementary colours, with apparatus and 

 diagrams illustrating their principal properties, he proceeded to con- 

 sider the nature of ocular spectra, which are always complementary 

 to the colours that occasion them. This he seemed inclined to consi- 

 der as the result of a natural effort in the eye to relieve itself from the 

 undivided influence of any one bright colour ; and he referred to the 

 beautiful structure of minute parallel lines, observed and figured by 

 Mr. Bauer, in his drawings of the part immediately over the retina. 

 These lines are governed by muscles which can alter their distance ; 

 and thus if the analogy between them and the colours of mother-of- 

 pearl or Barton's engraved plates may be admitted, allow of altera- 

 tions, which, excited by the influence of coloured rays entering the 

 eye, may cause the appearance of the complementary spectra. 



Mr. Brockedon advanced these suggestions very modestly, and only 

 as he said to excite others to inquiry. 



June 1 1 . — On the laws of coexisting vibrations of strings and rods. 

 This was one of the series of evening communications, given at this In- 

 stitution by Mr. Faraday, the matter and illustrations of which are sup- 

 plied by Mr. Wheatstone. The separate vibrations of a string as a whole, 

 or as subdivided by nodal points, were first shown, and then the co- 

 existence of two or more modes of vibrations in the same string, and 

 the consequent form of the string in different parts of its vibration, 

 illustrated by diagrams. Then the manner in which rods vibrated 

 either in the lowest or in any higher mode was shown, and reference 

 here made again to the coexisting vibrations, and to their combination 

 also with motion of a more general and ordinary kind. 



The experiments of Dr. Young were then referred to, in which he 

 observed the figure of the orbit described by any part of a vibratory 

 string, by remarking the line described by light reflected from it, after 

 which the Kaleidophone of Mr. Wheatstone was resorted to for further 

 illustration of these effects. This instrument consists essentially of 

 an elastic steel wire, twelve or fourteen inches long, fixed firmly in a 

 vice or foot at one end, and at the other furnished with a round me- 

 tallic bead. This serves as a convex mirror, and if held in the sun's 

 rays or near a single light, as a lamp or candle, reflects a spot to the 

 eye. When the wire is made to move, the spot describes an orbit 

 of various shapes according to the path of the end of the wire; and 

 if vibrations be inflicted on the wire, either by tapping it with the 

 finger or bv drawing a violin-bow along it, these are rendered visi- 

 ble, 



