172 



♦ KNOWLEDGE 



[Feb. 



1885. 



nmning, and swimming by their forefathers a few years 

 ago, is perfectly well known, but few of them could 

 bear any comparison with a savage as regards keenness of 

 vision at a distance. 



The President stated that Mr. Francis Cobb recollected 

 an instance, when he was in Africa, of a friend directing 

 attention to a small speck that he saw at a groat distance, 

 which he thought was moving. Oti pointing this out to 

 some natives who were with them, they at once pronounced 

 it to be the missionary, who was on foot, and his wife who 

 was on horseback, and mentioned who they were. Having 

 obtained a good binocular, Jlr. Cobb was able to see that 

 the natives were correct — that there were two persons — but 

 he could not, even with the binocular, tell one was riding, 

 nor who they were. 



The lecturer explained that deterioration of our poweis 

 of vision is due to two causes : — concentrating our atten- 

 tion almost exclusively on near objects — as in reading, 

 drawing, needlework, il'c. ; and never using our eyes for 

 any length of time in examining objects at a distance. He 

 particularly denounced small type schoolbotks as most 

 destructive of the sight, especially for very young children, 

 and then pointed out the best method of preventing 

 further mischief and of improving the vision. 



All schoolbooks should be printed in large type, and the 

 earliest books should be in type of the size used in printing 

 the texts hung in the waiting-rooms at railway-statiocs. 



Lessons should be given on the black-board, and pujiils 

 should be encouraged to describe objects at a distance. 



Parents should choose for their children who show a 

 tendency to shortsightedness, out-door occupations and 

 amusements. 



Prizes should be given at schools and athletic meetings 

 to the S3 who can accurately describe objects with which 

 they are unacquainted at the greatest distance. 



It would be ditKcult to overrate the value of this subject 

 and these suggestions. People who are short - sighted 

 cannot observe natural objects at a distance ; their attention 

 is confined to their immedi-ite surroundings. They must, 

 therefore, be deficient in many kinds of knowledge com- 

 pared with thoi^e who are more favourably circumstanced 

 as regards vision. 



It is not possible, without risking great injury to their 

 eyesight, to give shortsighted persons the same clear- vision 

 for a distance that is enjoyed by persons who have normal 

 vision, and, as Mr. Brudenell-Carter observed, all those 

 persons tcho are very sh.ort-s'ujh(ed, are on the threshold of 

 disease of the eye. 



In the discussion which followed Mr. Brudenell-C.^rter's 

 paper, I drew his attention to the great diliiculty I often ex- 

 perienced in getting many persons suffering from short sight 

 to wear spectacles. He made me this wise and witty reply : 

 " With regard to the unwillingness of short-sighted persons 

 to wear spectacles, he would mention an argument he 

 always used to the mothers of young ladies, which he found 

 extremely potent. He said, unless j'ou make the girl 

 grow up in spectacles, in the first place, she will never see 

 the expressions of the human face ; next, she will never 

 obtain the power of estimating character, and then she will 

 make a foolish marriage. He generally found that even 

 the most prejudiced were convinced by that argument." 



Mr. Brudenell-Carter has performed a national service 

 in bringing this important subject so prominently before 

 the public. 



The extent to which short-sighted persons go on in- 

 creasing their calamity is almost beyond belief. A great 

 number of them wear only a single pair of .spectacles, 

 with which they cannot see well either near or distant 

 objects, instead of having one pair of spectacles to read 



with and another for walking in, that is, for general out- 

 door use, as they should have. Others, again, content with 

 the fact that they can see any object plainly if they hold it 

 within five or six inches from the face, never wear any kind 

 of glasses, but hold up occasionally a single eye-glass or pair 

 of spring folders, far too strong for them when they require 

 to see any distance. Such a course of proceeding is usually 

 attended with disastrous results to the eyesight. 



It would require more space than I have at my disposal 

 to indicate the incalculable mischief done in cases of short 

 sight by persons who know next to nothing about their own 

 eyes, purchasing spectacles from those who know still less. 

 Unfortunately there are few opticians, indeed, who are 

 competent to assist the vision in cases of short sight : 

 until they understand both the eye and optics better, and 

 give their advice as a surgeon or physician would, with a 

 single-minded desire to preserve the eyesight of those who 

 apply to them for assistance, without regard to the profit 

 that can be made by selling their spectacles, defective vision 

 must increase. 



EAMBLES ^VITH A HAMMER. ■ 

 By "W. Jekome Harrison, F.G.S. 



iX SOtTTH LEICESTERSHIRE. 



rilHE slaty rocks of Charnwood Forest occupy the north- 

 X western part of Leicestershire. It is probable that 

 they are as old as any rocks exposed in England or Wales, 

 their formation dating back to PreCambrian times. These 

 ancient rocks dip to the south and to the east, passing under- 

 neath red marls and sandstones of Triassic age, which form 

 the greater part of the south and south-west of the county 

 e'f Leicester. These red rocks often have a banded appear- 

 ance, lines of bull" or drab alternating with the red beds 

 which constitute the mass of the formation. The upper- 

 most division of the Trias is known as the Keuper, because 

 in Germany ores of copper (Kupfer) are found in beds of 

 this age. Sections of the Keuper Bed Marls are well seen 

 in many of the cuttings of the Midland Pvailway north of 

 Leicester, as at Syston (where the red beds are traversed 

 by veins of gypsum) and between Loughborough and Trent 

 Bridge. The uppermost red marls with gypsum bands are 

 finely shown in the brick-pits at the foot of the Spinney 

 Hills, an eastern suburb of Leicester. Included in the 

 marls is an irregular sandy bed, called the Upper Keuper 

 Sandstone, about thirty feet in thickness. It is well ex- 

 posed in the Dane Hills, a low ridge which crosses the 

 Hinckley road, a mile-and-a-half west of Leicester. All 

 the strata of Triassic age — all which occur in England, at 

 all events — appear to have been deposited in an inland sea 

 of considerable extent, whose waters were almost constantly 

 saturated with common salt and with oxide of iron. To a 

 small percentage of the latter substance the red colour of 

 the beds is due, while the former compound is now the 

 source of the great supplies of rock-salt and of brine which 

 are obtained from the Trias of Cheshire and Worcestershire. 

 Evidence of the presence of an excess of common salt in 

 the waters of the sea which then covered Leicestershire and 

 all central England is afforded by the existence of numerous 

 pseudomorphs of salt in the red marl. These were 

 once cubical salt crystals, but water percolating through 

 the rocks has removed the salt — molecule by molecule — 

 and replaced it by marl, so that we now have perfect re- 

 productions, in hard marl, of the oriu'mal crystals. Such 

 pseudomorphs are common on the blocks of grey marl in 

 the Spinney Hill pits, and, indeed, may be found wherever 

 the upper red marls are exposed. They are best seen on 

 slabs that have been exposed for some time to the weather. 



