ill 



^ ^ 



1*1 





-:t 





656 



REPORT— 1884. 



from Madras on the Bay of Bengal to Bombay on the Arabian Sea will pive nn 

 average maxium difterence on quiet days of 7 volts ; between IJellavy and Beliraiun 



two inland statioTis east and west, 200 miles, an average of 2 or 2h volts ; betwop 

 Belgaum and Vingurla, a station inland and one on the sea coast, seventy miles, a 

 average of 2'.'> volts. l'er!iaps 1 00 or ] oO volts i ' ' ' ' 

 obtainable at tlH> widest limits on the earth's s 

 always been possible to measure the potential 

 * masrnotic storms,' but -JO volts per 200 miles is i 



average of 2'.'5 volts. Perhaps 100 or loO volts might be expected as the maxium 

 obtainable at tlH> widest limits on the earth's surface on quiet days. It has not 



difference occurring in SD-callcd 

 ■ magnetic storms,' l)ut ^JO volts per iiOO miles is not uncommon. 



As recent years have tauglit with what minute currents speech and telegraphic 

 symbols can be transmitted over long distances, the author suggests that thi' 

 time may be coming when these earth currents shall be made of service for such 

 purposes, and telegraphy shall in general benefit. 



It is found on disturbed days that actual reversals of the earth's currents take 

 place in a few minutes ; but that, certainly within a range of 900 miles, tiiesc 

 reversals all agree on ditferent lines; that is, all places east arc positive or negative, 

 at the same time, and places west of tiie opp;.bite sign simultaneously ; a large aveii' 

 is affected at the same time and in the same way. Great throbs art felt, which 

 increase or decrease the currents in all lines together like the beating of the pulses 

 •of the body. 



Seeing' tiiat during tlie passage of sunspots, the obscured portion of the earth's 

 surface is said to cease to receive heat, it may be conjectured tliat there will Iw 

 consequent inequalities iu the normal causes of dill'erence of potential, snllicient to 

 account for the strong currents, so inimical to telegraphy. Such phenomena nei'(l 

 not discountenance tlie theory above .set forth. 



16. Description of a Cijlindrtcal Slide Hale or Calciilatiwj Apiumitus. 



By Edwin Tiiacui:k. 



This apparatus corsists of twenty separate bars united in a frame whicli is 

 movable about a cylinder. The bars ])resent in sections ])rinted logaritliniic scales 

 of sixty feet, and of thirty feet radii. Thesfi bars read into the cylinder upon 

 which are printed two logarithmic scales of thirty feet radiuii eacii. In tliis appar- 

 atus the bars form slides and are worked similarly to the ordinary slide rule, thi- 

 open divisions of the scales giving live places of (igures instead of two as in th-' 

 ordinary rules. This rule ptrforras witii facility the solution of any question in 

 multiplication, division, and jjroportion of numbers, eith.er simple or fractional, with 

 or without powers and roots. 



17. 0)1 the Inconveniences of ike present Mode of quoting Scientific Journak. 



By Dr. H. BoiiNS, F.G.S. 



The author called attention to the inconveniences arising from tlie injudiciou-, 

 nnd arbitrary modes of quoting in iisi>, and suggested that:—!, livery .rounial 

 should bear its abridged title by which it is to be quoted on the title'page, in a 

 prominent position. 2. Tliat all quotations should use, if necessary, the full title, 

 or these abridged titles witli place, year, volume and page. 



18. An Accotuit of unusiml coloured Boivs observed in Fofj-f. 

 By Puu.ip Burton. 



It is well known that a luminous bow is sometimes formed in fogs by the 

 refraction and reflection of light in the particles of which they are composed. " Thh 

 nppearance, though sometimes nearly equal in size to the rainbow, is often perceptibly 

 smaller; and it differs from the latter also in not exhibiting any coloured rings, the 

 various colours being blended into a uniform whitish arch. 



Iksides the ordinary fog-bow wliich can frequently be seen, a fainter or super- 

 numerary one may also bo observed on rare occasions. This bow is smaller than 



