On the Light from organifed Bodies. 453 



Exper. 2. The laft experiment was then reverfed. A folution of one dram of Epfom 

 fait in one ounce of water, was brilliantly illuminated with mackerel light. Theni fix 

 drams of the fait were put into this luminous liquid ; and, after fliaking the phial very well 

 for a little time, to promote the folution of the fait, the light was totally extinguiflied. 

 But the fame light was again recovered, by the addition of fix ounces of water. 



In this manner the light may be frequently extinguiflied, and as often revived. In one 

 inftance, the fame light, by a repetition of this method, was made to undergo ten 

 extinctions. 



Exper, 3. A good quantity of herring-light, being mixed with a folution of four drams 

 of common fait in two ounces of water, was immediately extinguiflied. Then, fourteen 

 ounces of cold pump water were added thereto, and the whole liquid was at once 

 finely illuminated. On the next evening it appeared fl:ill very lucid ; and likewife on the 

 fucceeding night. 



Exper, 4. The experiment was reverfed. Half a dram of the fait, being diflblved in two' 

 ounces of water, had herring-light mixed therewith, fo as to be made very luminous. 

 On the addition of two drams more of the fait, the lucidnefs wrs inftantly deftroyed : but 

 the light was again recovered, by pouring eight ounces of cold water upon the extinguiflied 

 luminous fluid. The revived light was very vivid the next evening. 



Exper. 5. Two ounces of fea water were illuminated with mackerel-light, and then ex- 

 tinguiflied by adding two drams of common fait. The light was again reftored, by diluting 

 the folution with eight ounces of cold fpring water. 



N. B. If the illuminated liquid be uncommonly brilliant, it may fometimes require 

 more fait to extinguifli the light completely, than is here fpecified ; in that cafe, the 

 meafure of water for dilution, mull be always calculated in exaft proportion to the weight 

 of fait employed. 



SECTION VI. 



Spontatmus Light is rendered more vivid by Motion. 



EXPERIMENTS. 



Exper. 1. A quantity of illuminated liquid was poured into a broad veflel, which was 

 placed in the laboratory. The next evening, on examination, it appeared to be quite 

 dark. But a finger, or rod, being drawn through it, was followed by a luminous line. 



Exper. 2. A phial, containing a pretty large portion of liquid impregnated with light, 

 having been at reft a number of hours, the liquid feemed to have loft its luminous quality, 

 except a little glimmer floating at the top. It was then gently moved, and the light 

 diff"ufed itfelf gradually through the whole liquid : on agitation, the lucidnefs was much 

 incrcafed ; and, the briflicr the motion, the more vivid was the illumination. 



SECTION 



