286 



NATURE 



{yuly 28, 1 88 1 



fore, the light emitted by the coaietary matter exceeded 

 by many tmies the reflected solar light. I reserve for the 

 present the theoretical suggestions which arise from the 

 new information which the photographs have given us. 



The second evening of its appearing I examined the 

 head of this comet with a McClean spectroscope (with 

 slit) and also with a Hilgers half-prism instrument (a half- 

 size model of the Greenwich one). 



The appearances were mainly those seen by other 

 observers, viz., a bright continuous spectrum from the 

 nucleus and a much fainter one crossed by bright lines 

 from the coma. There were however two points of interest 

 which struck me, as I see by Nature, vol. xxiv. p. 261, 

 they did M. ThoUon in Paris. These were : («) The con- 

 tinuous spectrum from the nucleus had a mottled or 

 striated look, but I could not be certain whether dark lines 

 or bright lines or spaces predominated in causing this 

 effect ; (b) the 'presence of shorter and additional lines 

 to the three carbon ones, extending beyond the continuous 

 spectrum. 



These appearances, I admit, I only recognised indis- 

 tinctly and with doubt at the time, but, corroborated as 

 they now seem to be, I do not question that there was 

 some ground for them. With reference to the nucleus 

 spectrum it could only have comprised a small portion of 

 solar light as shown by the few Fraunhofer lines detected 

 by Dr. Huggins and others in it. The residue of the 

 bright stripe has been attributed (because continuous) to 

 some incandescent solid or liquid substance ; but is this 

 necessarily the case? Is it not possible that the matter 

 yielding this spectrum is still in a truly gaseous form, and 

 do not the appearances above described rather point to 

 the character of a gas spectrum passing from the line or 

 band condition to the continuous one, under its existing 

 circumstances of ignition, pressure, &c. (whatever these 

 may be).? — an ciTect not without parallel, I fancy, at least 

 in the case of hydrogen. J. R.A.ND Capron 



Guildown, July 23 



A COMET is now visible here. I saw it last Thurs- 

 day, June 30, at 3-10 a.m. It was in the west, and 

 appeared to me about 30° from the pole star, and 20" 

 above the horizon. The tail was straight and directed 

 towards the pole star. A local paper says this comet 

 was seen to the east at 8 p.m. the preceding day, and 

 that the tail was 20^ in length— it appeared to me only 5-. 



I regret I cannot send fuller information, but probably 

 the comet is to be better seen in England. 



Kardchi, July 2 F. C. CONSTABLE 



SEA-SHORE ALLUVION 

 TT is somewhat remarkable at the present day to find 

 ■•■ even professional men, when deahng with works of 

 coast defence, attributing the movement of littoral shingle 

 to the tidal currents. 



The late Mr. Palmer, C.E., in a well-known paper read 

 before the Royal Society nearly half a century back, 

 Col. Reid, R.E , in an essay published in the commence- 

 ment of the series of quarterly papers by officers in the 

 corps of Royal Engineers, Mr. Redman, M.Inst.C.E., in 

 a paper on the South Coast of England, read before that 

 society some thirty years back, and another on the East 

 Coast of England seventeen years back, as well as in 

 very numerous reports made by him for a Government 

 department (the War (jffice) during the last quarter of a 

 century, have all shown that these shingle formations are 

 in no way affected by the tide, which must exercise only 

 a negative influence, the flood and ebb setting in con- 

 trary and opposite directions, equal in duration, and 

 neutralising each other. Shingle moles are in effect 

 resultant on the wind waves alone, and are deposited in 

 two parallel ridges or hummocks locally termed "/w/A," 

 marking the relative range of neap and spring tides, the 



crest of the last being normally (except in some excep- 

 tional cases such as the Clicsil) ten feet above high water 

 of spring tides with a broad, gently sloping foreshore of 

 sand Jown to low water ; an abnormal tide, resultant on 

 exceptional gales occurring at rare intervals, sometimes 

 breaches the crest and produces great mischief, as at 

 Seaford on the Sussex coast a few years back, which was 

 inundated by the sea, and where the authorities are about 

 to carry out artificial works of defence. 



The prevailing movement in the EngUsh Channel is 

 to the eastward, or up Channel, due to the fact that south- 

 west winds prevail for nine months in the year ; and along 

 the East Coast the movement is southward, due to the 

 particular trend of the coast andthe North Sea offing. It 

 really hardly appears necessary to insist on these well- 

 known facts to any one practically acquainted with the 

 subject, or to hydraulic engineers conversant with the 

 surrounding physical conditions of our tidal harbours, 

 estuaries, and rivers. 



Notwithstanding this, strangely enough we find a con- 

 temporary journal, the Engineer, in a series of articles on 

 the Brighton, Hove, and Shoreham beaches, professedly 

 written for the education of public opinion on the subject, 

 themselves ignoring the fundamental laws governing 

 the motion of this marine alluvion, and attributing it to 

 tidal currents instead of to the wind waves, and yet in- 

 sisting at the same time that the question, as doubtless 

 it is, is an imperial one, demanding the attention of the 

 Legislature. 



Thus, October 3, 1879, "Brighton Beach" {The 

 Engineer) : — 



" A very strong tidal airrent sets up the Channel to 

 the eastward, and sweeps with it the rolUng shingle" ! 

 (sic.) 



" So rapidly did this disappear under the influence of 

 this current that it became necessary to stay its travel by 

 the erection of heavy timber groynes." 



" Knowing what we do also of the effect oi sea currents, 

 it is in our opinion exceedingly questionable if their 

 carrying powers can be arrested by anything short of a 

 check which shall produce almost dead water," 



One of the last papers read at the Institution of Civil 

 Engineers, on " Upland and Tidal Scour," also attributes 

 the movement of the Norfolk and Essex beaches to the 

 tidal currents. 



Nor are local authorities, highway boards, vestries, 

 district boards, and large landowners any more at 

 one than these would-be educators of public opinion 

 on the subject, for we find farmers as a rule sending 

 down their teams and waggons to the sea-shore during 

 winter slack time to collect boulders and pebbles from 

 the sea moles of Nature's forming ; railway companies 

 where allowed, and a convenient communication effected, 

 removing it wholesale for baUast of the iron road ; lords 

 of the manor conveying it equally wholesale to shipping 

 craft for ballast, until stopped by the strong arm of the 

 law brought to bear on the question by some Government 

 department. 



Local magistrates are equally offenders, as recently, 

 about twelve months back, the magistrates sitting at 

 Canterbury authorised their surveyor, after long discus- 

 sion, as the order was given with the fear of an impending 

 injunction hanging, " Damocles " like, over their heads, to 

 quarry shingle from the sea-shore at Heme Bay for the 

 repairs of the highways ; thus robbing the supply travel- 

 ling up the estuary of the Thames to the westward (the 

 general movement of the belt of shingle being diverted up 

 such estuaries as those of the Thames, Wash, &c.), the 

 material being at the same time so much wanted along 

 the Blue Town frontage at Shecrness, where grave fears 

 have long prevailed, due to the insufficiency of the sea- 

 shore works of defence. This Canterbury decision, taken 

 in the month of January in last year, appeared to us at 

 the time the extreme of rashness, when the interests to 



