104 On Peals of Thunder. 



he would 110 longer perceive a long continued rolling, but in 

 its place a single detonation produced by the union of the noises 

 of all the inushets. 



Surely it is not necessary to say more to enable every one to 

 comprehend the close connection there is between the thunder- 

 daps and the zig-zags of lightning. When a flash which is pro- 

 ceeding in a direction which abuts on the eye of the observer, 

 so folds itself as to appear for some instants in front, there is 

 enough to shew that an augmentation of the noise should be 

 the consequence. Nor is it less evident that this augmenta- 

 tion will be followed in its turn by a decided diminution, if, by 

 a second inflection, the lightning is again led away in the di- 

 rection of the visual line, and so on again and again. But not- 

 withstanding this, observations made with the purpose of put- 

 ting the intimate alliance between the zig-zags of lightning and 

 the peals of thunder Imong the number of demonstrated truths 

 would have a high interest, and may, therefore, be peculiarly 

 recommended to the attention of philosophers. 



Whoever has at all reflected upon the progress of the human 

 mind, will not attach much importance to theory, except in so 

 far as it is connected with observations, and the links which it 

 suggests and gives ; unless thus directed the satisfaction it af- 

 fords is small. The kind of merit at which we have just 

 hinted is, we will venture to say, possessed b}^ the theory we 

 liave offered of thunder. It in fact supplies us, if not with 

 the true lengths of the flashes of lightning, at least with evi- 

 dently the minirmtm valuations ; which, at all events, is some- 

 thing. Suppose a flash of lightning wholly situated on one 

 side of the zenith ; let us then draw two visual lines from its 

 two extremities ; supposing these two rays and the flash recti- 

 linear, they will form a triangle in which the eye of the ob- 

 server will be placed at the inferior angle. In every triangle 

 of this sort, one side is smaller than the sum of the other two. 

 We may estabhsh, then, the following inequality^ viz. that the r 

 visual ray between the eye of the observer and the most dis- 

 tant extremity of the flash is smaller than the sum formed by 

 adding the length of the flash to the length of the ray between 

 the eye and the nearest extremity of the flash. But iUwo quan- 

 tities are unequal, they will remain unequal when they both 



