Queries and Answer^s, 487 



active in growth, and most completely expanded, during the night ; and some, 

 from their extreme delicacy of structure, seem only fitted to blow in dark- 

 ness or twilight. 



The next question regards the motions of moles, dew-worms, and the 

 croaking of toads before rain. With respect to the first two, the motion 

 of the worm and its approach to the surface, account sufficiently for the 

 bustle of their natural enemy the mole. But what it is that actuates 

 the worm is the question. Here I can only offer a conjecture. The dew- 

 worm delights in humidity : it is necessary to its existence. But what in- 

 stinctive presentiment can the worms have that rain is about to fall ? They 

 seem to be sensible that a change is about to take place, nay, that it actually 

 has begun to take place ; for otherwise they could not be affected by it : and, 

 yet, we ourselves are seldom aware of the coming change. We must con- 

 clude, therefore, that there is an invisible precursor, which powerfully affects 

 them, which is unnoticed by us. Now, we know that, before the atmosphere 

 can discharge the water it holds in solution, it must be deprived of that agent 

 which makes it a solvent. This agent must be an invisible subtle fluid, per- 

 vading the earth as well as the air. As it descends or passes imperceptibly 

 away, we, indeed, can see minute drops of water deposited on cold and solid 

 bodies : leather and saline substances become moist ; the sky appears muddy 

 near the horizon ; misty clouds form on the tops of hills ; the lower stratum 

 of the air becomes more dense ; animals are restless ; the human frame is 

 languid, and any vitiated part of it aches with shooting pains. 



These are the visible and sensible indications of a change from dry to wet 

 weather, but which are by the bulk of mankind generally unnoticed ; and it 

 is only the meteorologist, whether philosopher or shepherd, who marks and 

 memorandums them. 



Our instruments (especially the barometer) are but imperfect : they have 

 not the fine sensibilities of the dew-worm, toad, &c. ; they indicate only what 

 is, not what is to be. The pressure of the atmosphere is more or less, 

 according to the depth of the aerial ocean, or according to its motion or 

 rarefaction, which lessens its ponderosity. Such changes the barometer does 

 show, but they are not always signs of either fine or foul weather. Ther- 

 mometers, as usually constructed, are most useful gages for indicating the 

 degrees and changes of temperature. Pluviometers, hygrometers, anemo- 

 meters, &c., are all useful adjuncts to the study of meteorology. But there 

 is an instrument still a desideratum in science, and, if such could be con- 

 structed suitable for practical purposes, it would be perfect as a weather- 

 glass. I mean an Electrometer ; not such as are only fitted for the study of 

 a philosopher, who has leisure to watch and observe the vibrations of gold 

 leaf; but such as would be an ornament, not " idly kept for show," on the 

 mantel-shelf of a farm-house. Such an instrument, that would indicate the 

 presence, quantity y direction^ and character of the electric fluid, is, I think, 

 everything we want, to make us " weather wise." By this we would know 

 when the solution of water in the air was going on ; when the air was fully 

 saturated ; when the water would again become condensed ; and, like the 

 worms, be able to apprehend, by a kind of prescience, when its descent to 

 the earth would take place. 



I therefore think, with respect to worms, toads, cats, and other animals, 

 that they are peculiarly sensitive of electric impressions, and that it is the 

 descent and character of that wonderful fluid, which warns or rather stimu- 

 lates the worm to rise from below to the surface of the earth : but how, 

 or in what manner the animals are affected, I must leave for others to 

 explain. 



Before I conclude, I beg leave to bespeak Mr. Gorrie's assistance in 

 explaining the use of the new instrument called, I believe, a differential 

 thermometer, and the true character of its indications. A " dew-point " is 

 spoken of: is this a point of nature, or of art? Is it produced by natural 



