Dec. 14, J 883.] 



• KNOWJ^EDGE ♦ 



359 



desired to leave £1,000 at his death, he would simply 

 have to calculate what amount he would have to invest 

 every year. 



But, first, life is only too uncertain to admit of such a 

 simple system as this ; and it required the ingenuity of man 

 to suggest a remedy by co-operation. A given area was 

 taken, and the number of deaths at various ages were 

 noted, and from these facts a table of the average duration 

 of the lives in the area at the various ages, generally called 

 a "Mortality Table," was drawn up. More recently the 

 experience of the mortality among the members of several 

 life assurances offices that had been established long enough 

 to make their experiences reliable was taken, and a 

 Mortality Table made out. Taking this last-mentioned 

 Table, we find that if we take several healthy boys of 14, 

 and several healthy men of 32, although all die at different 

 ages — some only living a few years, and some attaining to a 

 ripe old age — the average duration of the life of the boys 

 will work out to 46 years, and that of the men to 33 years. 

 Here then is the remedy for our difficulty, and if we deal 

 with the masses, and if several boys of 1 4 pay us premiums 

 of £1 a year during their lives, whether such boys' lives 

 happen to be longer or shorter than the average, we shall 

 with practical certainty not be losers if we agree to pay 

 each on death the amount that .£1 invested at com- 

 pound interest will produce in 4G years, or X96'5, for 

 one or other of them will pay us during their lives an 

 amount which, if invested at compound interest, will 

 produce that sum for each. And in a similar manner we 

 can deal with the men, only, as their lives have the shorter 

 duration of 33 years, we can only agree to pay each of 

 them £55. 



But secondly, the rate of interest is fluctuating, and not, 

 as has been assumed above, 3 per cent. ; and if the masses 

 be dealt with, there will be expenses of management to be 

 provided for, and, may be, occasional losses and bad debts. 

 With the most careful calculation it would, from their 

 nature, be difficult to equilibriate these items with mathe- 

 matical precision. Then, too, it would not be prudent 

 to trust too implicitly to the correctness of the tables. 

 Life assurance societies existing for the purpose of provi- 

 dent and not risky investment, and the ability to meet the 

 death claims made on them being of the first importance, it 

 is desirable and usual that these fluctuating items should 

 be more than covered, and this is done by the premiums 

 actually asked being greater than calculation may show to 

 be absolutely necessary. The result is that the boys and 

 men in our example would have to pay (say) 25s. instead 

 of 20s. a year. The profit made by premiums being ex- 

 cessive is divided every few years, — in a mutual office 

 among the assured, in an office having proprietors, among 

 the propri(!tors and the assured. In a mutual office, there- 

 fore, the assured are not hurt liy excessive premiums, the 

 excess being returned with interest. But in an office 

 having proprietors the assured will be affected by excessive 

 premiums in proportion to the amount of the profits to 

 which the shareholders are, by the constitution of the 

 office, entitled ; and in either office; the assured would be 

 affected if the division of the profits among them — the 

 distribution of " bonus " as it is called — is not equitable. 

 If, for instance, it is so arranged as in eti'ect to rob the 

 younger lives to make the older policies more valuable than 

 they ouglit to be. 



Aurora, 111., and Ogden, Utah, are, learns the Electrical 

 Review, lighted by electric lamps, the power used being 

 that of waterfalls. An electric lighting company proposes 

 to utilise the power of the Gene.see Falls at Rochester, 

 N.Y., and is putting in turbine wheels for the purpose. 



JRebietijS!. 



HOW TO SEE.* 

 By Richard A. Proctor. 



A FEW months since I met, for the first time, the great 

 and genial philosojiher Professor Fiske, of Boston, 

 Mass. He was so wonderfully cheerful, that I felt disposed 

 to ask a question akin to that asked in a well-known Bab 

 Ballad, of the Gentle Pieman, 



" Why so very very merry, 

 Is it purity of conscience, or your one-and-Beveu sherry ? " 



I refrained, however; and he presently explained. "I 

 have been revelling this morning," he said, " in a new pair 

 of spectacles : " which struck me as almost as odd as revelling 

 in one-and-seven sherry, till he explained that for years he 

 had been troubled by ill-suited spectacles, and that " our 

 friend Mr. Browning " had at a first trial provided him 

 with a perfect pair. 



In the book before us, Mr. Browning shows how he manages 

 thus to correct imperfect vision, nay, how cases more difficult 

 than Professor Fiske's can be satisfactorily dealt with. (He 

 mentions that particular case at pp. 02, G3.) The book is 

 full also of useful hints and suggestions about the eyesight 

 generally. He points out, truly enough, that sight, the 

 most precious of our senses (for if we have sight we can 

 both speak and listen, even though deaf and dumb), is 

 allowed to become impaired and all but lost before skilled 

 advice is sought for, whereas for the least defect of hearing 

 a surgeon is consulted. 



Although a portion of the work appeared in these 

 columns, the greater part is new — and we believe readers 

 of Knowledge would have been glad to get the work even, 

 if it had only contained what appeared here, so useful was 

 the information there brought together. 



I am myself particularly interested by what Mr. 

 Browning says respecting his way of dealing with eyes of 

 unequal focal length. My left eye is simply useless for 

 distant objects, though of marvellously sharp vision for 

 objects close by. My right eye is of the usual average focal 

 length. I can fully confirm the statement of one who con- 

 sulted Mr. Browning about such disparity of vision, that 

 spectacles abruptly correcting it cannot be worn without 

 distress for more than a few minutes. How Mr. Browning 

 worked up to a satisfactory solution of the problem — is it 

 not recorded in the book before us ? I shall certainly try 

 this way of doing what all my life I Iiave failed to do — to 

 see, namely, with both eyes at once. 



Every one who cares about his eyesight should get this 

 little book : those who think their eyesight of no particular 

 moment can very readily dispense with it. 



NATURE'S ENERGY.! 



This is at once a very useful and a highly interesting 

 little work, holding a place midway between such works as 

 in former times Neil Arnott and Dionysius Lardner wrote 

 about physical matters, and the technical and, to say the 

 truth, rather dry treatises in which the same subjects have 

 been discussed by some of our modern physicists. Mr. 

 Carpenter, son of one of the most eminent men of science 



* " How to Use onr Eyes." By John Bro>viung, F.E.A.S. (Messrs. 

 Chatto & Windus, London.) 



t " Energy in Xaturc : a course of six lectures upon the Forces 

 of Nature and thoir mutual relations, delivered under the auspices 

 of the Gilchrist Educational Trust. By \V. L. Carpenter. (Messrs. 

 Caseell & Co., London.) 



