40 



• KNOWLEDGE • 



[Jan. 19, 1883. 



their lalwurs ; tlie brain is ever active in some or otlier of 

 its parts. If we learn that in twenty-four hours a man's 

 heart performs work equal to 1:24 foot-tons— that is, the 

 total force it expends in its work of twenty-four hours, 

 would raise l'2i tons 1 foot high — we may form some ade- 

 quate idea of the basis on which rests the truth that the 

 idleness of everj--day life is not exempt from physiological 

 work of a grave and heavy kind. 



An adult human body, in perfect health, is thus seen to 

 lose substance each moment, in the ordinary acts of life. 

 It is clear that there must exist a limit to this loss. 

 Pursued to extreme limits, the body would waste away 

 entirely. We grow thinner after work, and the difference 

 between physiological and well-nigh inappreciable thinness, 

 and that material decrease which becomes visible to the 

 eye, is only one of degree after all. Hence we begin to 

 perceive that the repair of this wear and tear must be as 

 incessantly taking place as is the loss of substance itself. 

 We also see that /ood-fakinff is the plain means whereby this 

 loss is made food. " Food," is only matter containing the 

 elements of the body in a more or less easily assimilated 

 form, and through which we replace the substances which 

 have disappeared from our bodies in the work which the 

 act of living entails. Hunger and thirst are nature's 

 warnings that the loss must be repaired. They resemble 

 the automatic danger whistle of the engine or the ring of the 

 fire-alarm, which acts as a warning that instant attention 

 is needed to a source of possible danger — this danger in 

 the case of our bodies, existing in the weakness which 

 would ensue from the non-repair of our bodily sub- 

 stance. A healthy man, then, whose outgoings in the 

 way of waste (the result of " work " of one kind or 

 another) equal his incomings in the shape of " food," 

 shoiild neither gain weight nor lose it. As a matter 

 of fact, this issue is borne out by the observation of the 

 body in health. Life, viewed in this aspect, is in reality a 

 kind of bookkeeping by single entry. One column contains 

 the income, consisting of food in the shape of air, water, 

 and solids — whereof flesh-forming matter, starch, sugar, 

 fats, and minerals are the chief constituents. The other 

 column contains the expenditure, which consists of water, 

 carbonic-acid gas, ammonia, urea, and other matters. 

 A calculation of the physiological "business" would 

 show us that about ^^ lb. of matter are absorbed, 

 whilst about S^ lb. are given off as waste matter per 

 day, in the healthy adult economy. The profit con- 

 nected with this important transaction, is represented 

 by the energy or the poiver of doing work we obtain from 

 our food. It may be interesting to point out that a calcu- 

 lation gives the amount of energy exhibited by an adult 

 man in twenty-four hours as equal to about 3,-1:00 foot tons 

 — a force equal to that required to lift that number of tons 

 one foot high. Of this amount of force, about one-tenth 

 is expended in our varied movements. The residue seems 

 to be occupied in the production of heat. And the 

 amount so expended in " keeping ourselves warm," is re- 

 presented by power sutlicient to raise a man's body (weigh- 

 ing about 150 lb.) to a height of 8i miles. So we discover 

 that a human body is the seat and origin of an amount of 

 energy which, but for the exact experimentation on which 

 these data ha^e been founded, would almost defy belief. 



DuEiXG the recent storms, the %\-ind-pressure plates 

 erected on the Forth, under the orders of the engineers of 

 the Forth Bridge, have indicated a maximum pressure of 

 20 lb. per square foot of the smaller plate of 2 square feet, 

 while the large heavy plate of 300 square feet has indicated 

 but 12-5 lb. per square foot 



LECTURING NOTES. 



By Richard A. Proctor. 



FIVE courses of lectures for the Oilchrist Trust were 

 commenced by me last week, at Leicester on Monday, 

 at Lincoln on Tuesday, at Chesterfield on Wednesday, at 

 Doncaster on Thursday, and at York on Friday ; the re- 

 maining lectures will be given in due course, by Dr. W. B. 

 Carpenter, F.R S., IMr. W. Lant Carpenter, the Rev. Mr. 

 Dallinger, and Professor Martin Duncan. At all the 

 places named there were crowded, attentive, and kindly 

 audiences. At Leicester hundreds were turned away from 

 the Temperance Hall, at Lincoln the large Corn Exchange 

 was filled (about 2,000 were present), at Chesterfield and 

 Doncaster there were similar crowds, and lastly, at York, 

 the bUls in the streets announced that no more tickets re- 

 mained (for course tickets an advance of 400 per cent, on 

 the original price was offered). It is well to see that the 

 bequest of Mr. Gilchrist is thus appreciated. 



Although it has been no new experience to me to address 

 most kindly and attentive audiences in this part of 

 England, I must confess it seems to me significant of good, 

 that, with so absurdly low a charge as one penny for ad- 

 mission, no disturbing element should ever be present at 

 these Gilchrist gatherings. That among from a thousand 

 to two thousand auditors there should be apparently not 

 one who has not come to listen for more than an hour 

 attentively to talk about astronomy, or geology, or elec- 

 tricity, is interesting, even in such large cities as Leicester, 

 Lincoln, and York. But that having come, not one 

 should tire of what must be new and strange to many, 

 seems to me still more noteworthy. I must confess that 

 had I seen a score or more filing out towards the end of 

 the lecture, I should have been little surprised ; for the 

 only way in which scientific food is at all prepared for 

 readier digestion in these lectures is by the omission of 

 technicalities. The rule assigned to Knowledge is the rule 

 I have ever followed in lecturing, — simply to give "science 

 plainly worded but exactly described." It has ever seemed 

 to me that oratory is out of place on the lecture platform. 

 The truths of science are of themselves so impressive that 

 they need no tricks of eloquence or fine speaking — which, 

 indeed, serve but to obtrude the petty personality of the 

 lecturer between his hearers and the grand teachings of 

 nature. And speaking of the lecturer's personal feel- 

 ings, I may remark that, in my opinion, the greatest 

 compliment an audience can pay a lecturer on science 

 is to restrain (during the discourse) the applause their 

 goodwill would offer him, that they may the better 

 attend to what he is telling them. Applause at the 

 end comes all the more effectively and pleasantly, though 

 unfortunately, so far as my own subject is concerned, it 

 comes at a time when the lecturer recognises to the full his 

 utter nothingness in relation to what he has been saying. 

 He feels that one might as well applaud the wind for the 

 music of the yEolian harp, as the lecturer for the grandeur 

 of the truths of science. 



EsGixEERiXG AND Metal Trades Exhibitios. — Under 

 this title, a large and very important exhibition is to be 

 held in the Agricultural Hall, London, from July 5 to the 

 21st of this year. It will comprise specimens of engineering 

 and mechanical work of almost every kind. Like the 

 highly successful Naval and Submarine Exhibition of last 

 year, the present undertaking is entirely the work of Mr. 

 Samson Barnett, jun. The short time during which the 

 Exhibition will be open is scarcely a drawback — at least 

 from a business point of view, as many of last year's 

 exhibitors can doubtless testify. 



