Aug. 1.5, 1884.] 



♦ KNOWLEDGE 



129 



crystalline alkaloid, the theine, a compound belonging to 

 the same class as strychnine and a number of similar vege- 

 table poisons. These, -when diluted, act medicinally, that 

 i.s, produce disturbance of normal functions as the tea 

 does, and, like tlieine, most of them act specially on the 

 nervous system ; when concentrated they are dreadful 

 poisons, very small do?es producing death. 



The non-tea-drinker does rot sutler any of these five 

 o'clock symptoms, and, if otherwise in sound health, remains 

 in steady -n-orkiDg condition until his day's work is ended 

 .and the time for rest and sleep arrives. But the habitual 

 victim of any kind of drug or disturber of normal functions 

 acquires a diseased condition, displayed by the loss of 

 vitality or other deviation from normal condition, wliich is 

 temporarily relieved by the usual dose of the drug, but 

 only in such wise as to generate a renewed craving. I 

 include in this general statement all the vice-drugs (to coin 

 a general name), such as alcohol, opium, tobacco (whether 

 smoked, chewed, or snufted), arsenic, haschisch, betel-nut, 

 coca-leef, thorn-apple, Siberian fungus, mate, itc, all of 

 which are excessively " refreshing " to their victims, and of 

 which the use may be, and has been, defended by the same 

 arguments as those used by the advocates of habitual tea- 

 drinking. 



Speaking generally, the reaction or residual effect of 

 these on the system is nearly the opposite of that of their 

 immediate efl'ect, and thus larger and larger doses are 

 demanded to bring the system to its normal condition. 

 The non-tea-drinker or moderate drinker is kept awake 

 by a cup of tea or coffee taken late at night, while the 

 hard drinker of these beverages scarcely feels any effect, 

 especially if accustomed to take it at that time. 



The practice of taking tea or coffee by students, in 

 order to work at night, is downright madness, especially 

 when preparing for an examination. More than half of 

 the cases of break-down, loss of memory, fainting, kc, 

 which occur during severe examinations, and far more fre- 

 quently than is commonly known, are due to this. 



I frequently hear of promising students who have thus 

 failed ; and, on inquiry, have learned — in almost every 

 instance — that the victim has previously drugged himself 

 with tea or coffee. Sleep is the rest of the brain : to rob 

 the hard-worked brain of its necessary rest is cerebral 

 suicide. 



My old friend, the late Thomas Wright, was a victim of 

 this terrible folly. He undertook the translation of the 

 "Life of Julius Caesar," by Napoleon III., and to do it in 

 a cruelly short time. He fulfilled his contract by sitting 

 up several nights successively by the aid of strong tea or 

 coffee (I forget which). I saw him shortly afterwards. In 

 a few weeks he had aged alarmingly, had become quite 

 bald, his brain gave way and never recovered. There was 

 but little difference between his age and mine, and but for 

 this dreadful cerebral strain, rendered possible only by the 

 alkaloid (for otherwise he would have fallen to sleep over 

 his work, and thereby saved his life) he might still be 

 amusing and instructing thousands of readers by fresh 

 volumes of popularised archaeological research. 



I need scarcely add that all I have said above applies to 

 coffee as to tea, though not so seriously in tins coitntrt/. 

 The active alkaloid is the same in both, but tea contains 

 weight for weight about three times as much as coffee. In 

 this country we commonly use about 50 per cent, more 

 coffee than tea to each given measure of water, and thus 

 get about half as much alkaloid. On the continent they 

 use about double our quantity (this is the true secret of 

 " Coffee as in France "), and thus produce as potent an 

 infusion as our tea. 



I need scarcely add that the above remarks are exclu- 



sively applied to the habitual use of these stimulants. As 

 medicines, used occasionally and judiciously, they are in- 

 valuable, provided always that they are not used as ordi- 

 nary beverages. In Italy, Greece, and some parts of the 

 East it is customary when anybody feels ill with indefinite 

 symptoms to send to the druggist for a dose of tea. From 

 what I have seen of its action on non-tea-drinkers it appears 

 to be specially potent in arresting the premonitory symptoms 

 of fever, the fever headache, itc. 



\\ 



OPTICAL RECREATIONS. 



Bv A Fellow of the Royal Astroxomical Society. 



( Continued /rom page 47.) 



7E may fitly conclude our few remarks upon lenses 

 f by a description of the methods adopted to find 

 their foci, which the amateur will often find very useful. 

 First, in the case of a convex lens of any considerable size, 

 a cardboard disc may be fitted at the end of a straightedge 

 accurately graduated into feet, inches, and tenths of an inch, 

 at right angles to its length. This arrangement is then 

 taken out into the sunshine, and the lens whose focal 

 length is to be measured is slid along the straightedge 

 rigidly parallel to the screen, until a sharp and distinct 

 image of the sun is formed upon the latter. The distance 

 between the point where the middle of the edge of the lens 

 rests on the straightedge and the screen may then be taken 

 off' the scale by mere inspection. Or, suppose that we wish 

 to find the focus of our lens when sunlight is not available. 

 We place a lighted candle at the end of a graduated scale 

 of inches and parts, and so connect the lens with the scale 

 that it may always have its axis parallel with the edge of 

 the scale as it slides along it. A card disc, or screen, must 

 also be made to slide along the scale so as to be in a line 

 with the light and the lens, the light being manifestly on 

 one side of the lens and the card on the other. Both the 

 lens and the card must now be shifted backwards and for- 

 wards until the least distance between the light and the 

 card is found, at which a sharp image of the candle is 

 depicted on the latter. Then, if we measure this least 

 distance accurately, it is four times the focal length 

 of the lens. An ingenious modification of this method 

 devised by the Rev. Prebendary Webb, and applicable 

 to the measurement of the foci of the smallest 

 lenses, is illustrated in Fig. 22, in which K N is a 



Fig. 22. 



knitting-needle, along which three perforated corks, 

 C, C, C", slide. To the one in the middle, C, the lens, L, 

 whose focus is to be measured, is attached in a vertical 

 position, with its axis parallel to K X ; while in each of the 

 two others is stuck a piece of an ordinary sewing-needle, 

 n, n', point uppermost, and of such a length that a line 

 joining the two points p shall pass, as nearly as can be 

 managed, through the centre of the lens, L. Now, as in our 

 previous experiment, the corks are moved backwards and 

 forwards until the inverted image of the needle-point, n', 

 formed by the lens is seen coincident, and equally distinct, 

 with the point of the needle, n, when both are viewed 

 through a pretty strong magnifier, L', by the eye at E. If 

 this condition of things obtains when the needle-points are 



