s66 Changes of Colour and DlrtSlion in Thunder-Clouds, 



I was called at five o'clock in the morning. The (ky was then covered with clouds, not 

 very denlV except to the fouth, and flying with great rapidity to the \V. by S. or W. S. W, 

 It lightcjied very frequently in the N. W. and S. W. quarters, by doubled and trebled flafhes 

 of a bright illumination (for the adlual fladi was not fecn), with very loud thunder, ufually at 

 the interval of 1 1 or 12 fccon Js after the (ladi. The lower prominences, or ragged extremities- 

 of the clouds, were conftantly tinged with red, and I was informed that they had been very 

 much redder before I got up. 



At about tjn minutes after five, no rain having fallen, but a few heavy drops, a fuddea 

 darkncfs came on, and the dufl rofe in Ncwman-flreet, where I refide, begijining at the 

 fouth end, about 250 yards diftant from my houfe, and proceeding to tlie north. It was 

 rery denfe, and rofe to the height of about fixty feet by eftimate, which is much higher than 

 the houfes in the ftrect. At about a quarter pad five, the darknefs being then greaiell, the 

 houfes on the oppofite fide of the ftreet appeared as if feen through a deep blue glafs, par- 

 ticularly the white flone work above the windows ; and upon looking upwards, the clouds 

 were feen of a deep leaden blue colour, and moving fwiftly in a diredion precifely oppofito 

 to that before obferved, namely, to the E. by N. or E. N. E. Soon afterwards, the light- 

 ning and thunder continuing during the v.'hole of thefe changes, there fell a heavy Hiower, 

 which heat againft the weftern face of the houfe, and the darknefs gradually went off. At 

 half pad five the clouds were much higher, and moved with a moderate angular motion 

 to the north, while the fmokc of a chimney oppofite my window was gently driven to the 

 fouth. 



We have yet much to learn concerning the theory of thunder-dorms. It is well known 

 by experiments with the electrical doublcr *, that almoft all bodies poflefs a certain degree 

 of eleftrization, which is variable from a confiderable number of circumftances. It is alfo 

 known from Franklin's experiments of the can and chain, as well as from numerous other 

 fafts, that the imenfity of the eleftric date will be augmented by diminifhing the furfaces of 

 bodies. In this way, as well as from other caufes, it is inferred that clouds become highly 

 eleftrificd during the progrefs of their condenfation ; fo that flafhes of lightning pafs be- 

 tween them and the earth, and between each other. From other obfervations and deduc- 

 tions, it has been alfo rendered highly probable that the long range of clouds in a dorm 

 of this nature does ferve as a condu£lor, through which flalhcs of eledlrie fire are conveyed 

 from one part of the earth to another part in a different date. The fads above dcfcribed 

 feem uncommon, and, if collated with other more ufual events, may afford fome indruc- 

 tion concerning this clafs of phenomena. I do not highly edeem the conjectures which pre- 

 fent themfelves to me on this occafion ; but fliall communicate them, becaufe they tend to 

 point out future objects of refearch. 



The Angularity of this thunder-dorm appears to have arifcn from the mafs of aque- 

 ous vapour having been much too fmall to afford a favourable communication between 

 the two oppofite dates of eleftrlcity on the furface of the earth. If the mafs of clouds be 

 fuppofcd to have been at fird near the eadcrn portion of the earth, and to have become 

 eleftrified and repelled, they would, on the common principle of bodies in that date, be re- 

 pcllci^ and pafs fwiftly to the wedern part of the furface to depofit their eledlricity as foon 



• New Experiments on Elcflricity. By the Rev. A. Bcnnct, F.R.S, oiSkavo. London. 



