1 o AViu ElfStical Iiijtnimtiit. 



but it .would have difappcarcil totally, if the want of pcrfed fiatncfs in tnc cloth had no*; 

 prevented its being inclined beyond a certain angle with regulnvity. The branches of the 

 crofs at right angles to the inclined wires alfo nearly vanlllied. 



But when the warp or longitudinal wires were inclined to the axis of- vifion, the images 

 were altered in their relative brightnefs and pofition, in a manner which it would be toa 

 prolix to relate. Tliefe changes terminated in an hexagon with fix radii, as in Fig. 12. when 

 the inclination was about 45 degrees. In this, aS in all the changes, the ipcdlra were co- 

 loured with the red farthell from the centre, and they all pointed to the centre. Tliis 

 unexpeded appearance led to an examination of the cloth by a fimple magnifier in both 

 tjofitions of inclination, when it was found, that in the firft defcribed pofiiion die inter- 

 ftices of the wires appeared to be nearly long fquares, or parallelograms ; but in this lad 

 defcribed pofition the threads of the warp being in reality bended by the operation of weav- 

 ing over the weft, in angles of about 35° out of tlie plane, did apparently meet, fo as to 

 leave apertures of the form of equiangular triangles, and no doubt caufed the hexagonal 

 combination in Fig. 12. 



After this imperfeft defcriptlon of a phenomenon of fome curiofity, I mud decline en- 

 tering into any difcuflion of the confequences to which it feems to lead. Sir Ifaac New- 

 ton's Experiments on InfleiSlion, with the edges of two knives, are fimple, and at firfl; con- 

 fidcration do not appear difficult to be underftood. Yet, fimple as they arc, there are cer- 

 tainly many variations yet to be made, and admeafurements to be taken, before tlic popular 

 explanations of the mutual agency of bodies and light upon each other can be admitted 

 •without hefitation. This pr»)cefs of examination afFords fome peculiar facilities, on account 

 of the great quantity of light which is fimilarly affe£ted, and the pothbility of applying a 

 magnifying power and micrometer. Subfequent meditation may perhaps fugged the caufc 

 why the radii in thefe figures are triple, and parallel to each other, while all the fpectra indi- 

 vidually diverge from a centre : but 1 have rather chofen to refer them as they are to the ex- 

 amination of philofophers. And I am tiie more induced to hope that this examination will 

 be made, when it is confidered, that the appearance prefents itfelf through any fine muflin or 

 cambric to the naked eye, though Hill better with the opera-glafs or perfpedives, which are 

 in the hands of every one, and that the wire -cloth of fine fieves or wine-ftrainers is a ma- 

 terial eafy to be procured. 



III. 



Defcriptiin of an Injlrument luhich renders the EleBr'idiy of the Almofphere nnd other weai 



Charges very perceptible, without the Poffbility of an equivocal Rejiitt. 



XN the year 1787, when the eledrical doubler engaged the attention of philofophers, for its 

 adoniljiing power of magnifying the minuted quantity of fimple eledricity, and the fubfc- 

 quent difcovery of its fpontaneous elcdricjty had greatly reduced its apparent utility, 1 

 had the pleafure of a converfation witli the Reverend Abraham Bennet, of Wirkfwortli, 

 the inventor, who flicwed me his method of depriving this inftrument of much of its adhe- 

 rent eledricity, by ivorking it for a time with all its parts in communication with the earth. 

 But at the fame time he remarked, that if he were to make an indrumcnt in which this 

 7 eledricity 



