216 Dr Brewster on the motions of the Molecules of Bodies. 



ed,"** says Dr Drummond, *' to be in constant motion, appa- 

 rently rolling upon their axis, but having no degree of pro- 

 gressive movement. The light reflected from their surface was 

 very brilliant, like that from polished silver, and often disap- 

 peared, and again returned, with alternations so rapid, as to 

 produce a twinkling very like that of a fixed star. 



** Sometimes on examining an individual specimen it would 

 disappear altogether, but in a few minutes return, renew its 

 twinkling and apparent revolution on its axis, and again dis- 

 appear to return as before. 



" Frequently, also, some were observed to be in the fluid, or 

 on its surface, for a long time motionless, but very brilliant ; 

 then they would give a few slight twinkles, seem to turn round, 

 and almost disappear ; then resume their original situation for a 

 moment, appear more brilliant than at first, partly disappear 

 again, and again return, and so on for a number of times, till 

 at length they would disappear entirely ; but after a time (per- 

 haps five or ten minutes) show themselves in the same spot as 

 before. These observations could be made only on the larger 

 spicula; the minute ones being in incessant motion. 



" I'he motion continues in a great many of the spicula even 

 after the fluid containing them has become putrid ; but it is 

 then more slow. The addition of ardent spirits deadens but 

 does not destroy the motion. After exposure to a heat of 

 boihng water, the number of spicula seems much diminished, 

 and those which remain move less rapidly than before. The 

 addition of vinegar, in a quantity equal to the fluid contain- 

 ing the spicula, suddenly causes a great diminution of the 

 number of moving ones, probably from coagulating the albu- 

 minous matter which had been washed from the eye along 

 with the spicula, and entangling them in it. Many, however, 

 continue their motion as before. 



" The spicula of the eye of the herring are jointed, being ge- 

 nerally thus divided into three distinct portions, of which that 

 which forms the centre is much larger than the two others. 

 In common daylight, the entire spiculum is silvery ; but if it 

 be observed in the sunshine, it will be found to reflect differ- 

 ent rays from the jointed portions ; the end joints being gene- 



