286 Mr. Ainger on the 



ence, because each drop in the shower (with an exception to 

 be presently noticed) would transmit rays of every coloured 

 light, producing by superposition with themselves, and with 

 the rays from other drops, the sensation of white light, differ- 

 ing only in brilliancy from that reflected at the outer surfaces. 

 Mere divergence will not, I think, affect, to the extent sup- 

 posed, the apparent quantity of light derived from numerous 

 points at a great distance. It is true that a parallel pencil 

 would appear very bright at a distance, which would render a 

 divergent pencil, of equal magnitude, quite insensible. But, 

 in the case under consideration, it is not a single pencil of 

 parallel rays which is compared with another of divergent 

 rays ; the eye views a luminous space, part of which is so 

 distant, that a thousand drops might be contained in a line 

 having an inappreciable angular value. If the light from 

 each of these thousand drops proceeded in parallel lines, the 

 eye, although it would receive all the light transmitted by 

 some one drop, would lose all that was reflected by the others. 

 If, on the contrary, the light diverged from the drops, the eye 

 would receive only a very small portion of the light from the 

 one drop, but it would now receive an equal portion of the 

 light reflected from each of the remaining nine hundred and 

 ninety-nine drops ; the whole of which proceeding from a 

 space of no sensible magnitude, would produce a general 

 impression of illumination, notwithstanding that the light from 

 any single drop might have been invisible. An instance of the 

 effect produced by numerous simultaneous impressions, each 

 individually imperceptible, is furnished by a room in which 

 silkworms are feeding. A hundred of these animals emit no 

 sound that the ear can detect ; but the noise of a very large 

 number in the act of eating has considerable intensity. In 

 a large and crowded theatre no individual is heard to open 

 a play-bill, or turn the leaf of a book ; but if any circumstance 

 occasions a large portion of the audience to do either of these 

 nearly at the same instant, a noise is produced like the rushing 

 of a torrent. The correct statement, therefore, I think, would 

 be, that in addition to the reflexion from the anterior surfaces, 

 which is common to all the drops in the shower, every drop, 

 with the [exception before alluded to, is rendered visible by 



