Intelligence and Miscellaneous Articles. 397 



Park Farm belongs to that deposit. Granting, however, that the 

 loam in the latter case is really Chillesford clay, the author stated 

 that it is probably carried under the Wangford Crag by a northern 

 dip. Thus he considered that neither of these sections contains 

 indisputable evidence of the superposition of the Chillesford clay to 

 the Fluviomarine Crag. He also expressed a doubt of the crag at 

 Bulchamp being a continuation of the Wangford bed, and stated 

 that it much more resembles the Mya-bed as seen at Yarn Hill. If 

 this interpretation be correct, Chillesford clay might occur at 

 Henham Park Farm intermediate between the Crag of Wangford 

 and the Mya-bed at Bulchamp. 



LII. Intelligence and Miscellaneous Articles. 



ON THE BRITISH-ASSOCIATION UNIT FOR ELECTRICAL MEASURE- 

 MENTS. BY W. H. PREECE. 



To the Editors of the Philosophical Magazine and Journal. 



Electric and International Telegraph Company, 

 Gentlemen, Southampton Station, April 15, 1867. 



T BEG to suggest, through your columns, to those physicists and 

 -*- electricians who have adopted the British- Association unit for elec- 

 trical measurements, that in place of expressing this unit, as is va- 

 riously done at present, by 



B,A. unit, 



Ohmad, 



Ohm, 



10? metre &c 

 second 



it would be very convenient to adopt some universal symbol analo- 

 gous to that used for degrees (°). 



The Greek letter vu appears to me very convenient, not only from 

 its similarity in name, but from its comparative freedom from general 

 use as expressive of any particular function or quantity. 



Moreover it offers a simple and admirable method by which we 

 may distinguish conductivity from insulation resistance — a source of 

 great inconvenience at present — by joining the small letter (w) to 

 the former, and the capital (£1) to the latter. Thus, instead of dis- 

 tinguishing the two as is now done, by an immense series and rows 

 of figures, or, as is proposed to be done, by calling the one Ohm, 

 and the other Megohm or Milliohm, we should have 



r> a •*. irv7 metre 



a ui = a B.A. units or 10 , 



second 



a® = a B.A. units X 1,000,000. 

 The conductivity of the Atlantic cable would be given by 



7524 w , • 

 and its insulation by 



2349 Q per knot, 

 which may still be read Ohm and Megohm. 

 . The advantage of such a symbol to practical men is immense. I 



