Jan. 20, 1882.] 



KNOWLEDGE 



249 



data on which predictions were founded, notably Hamescy's 

 " Astroloj^a Mundi," it was the conjoined influence of tlio sun 

 and planets, rather tljan the moon's position relative to the earth, 

 which was mainly relied on as causing atmospheric changes, and what- 

 ever nucleus of truth the system contained was necessarily obscured 

 and rendered almost valueless by the imi)erfect observation and 

 boundless credulity of the times. And, in tho second place, it must 

 be clear to every tyro in natural science, that if it be rational and 

 in accordance with the verifications of science, to assert that tho 

 moon's influence acts upon the waters of the ocean, it cannot bo 

 foolish and irrational to hold that the same influence affects the 

 waters of the clouds and the air in which they float — both ponder- 

 able bodies equally subject to the laws of gravitation. So much 

 may be taken for granted. 



But the most tangible objection urged against the theory of lunar 

 influence is that atmospheric changes are not coincident — or, if so, 

 only accidentally— with changes of tho moon, and, therefore, it is 

 unreliable. This reasoning, however, is in itself fallacious. Those 

 who predict changes in the weather from the moon's influence, 

 allege that the disturbing force is felt when she is on the equator, 

 crossing from north to south declination, or, life I'frst'i, arriving at 

 one of the stitial colnres at its extreme north or south declination. 

 And, of course, she may or may not at such times be at the points 

 called syzygies (tho new or full moon), or at the quadi-atures. 

 Thus, an atmospheric change is not necessarily to be expected at 

 every change of the moon ; but it may reasonably be when slio 

 arrives at one of the cardinal points, and it is found by experience 

 almost invariably to occur. 



But, without the knowledge of what the theory really is, the most 

 acnte critics mnst fall into error in judging a system whose principles 

 they misapprehend. To give a striking instance — It is asserted by 

 no less an authority than Professor Jevons, in his Science Primer, 

 " Logic,' that the belief in lunar influence on the weather is an 

 illustration of " fallacy." He says : — " In one sense it is a fallacy 

 that the moon governs the weather, because long and careful 

 enquiries have sho^vn that there is no correspondence between 

 changes of the moon and clianges of the weather." This i-easoning 

 clearly shows how the subject is misunderstood by those who accept 

 the popular notion of the theory. Certainly, a change need not be 

 expected if the syzygies and quadratures are alone regarded. The 

 same writer says furtlicr ; — " There are at least twelve new moons 

 in each year, and changes in the weather take place in this country 

 at least once a week on an average. It is, therefore, quite likely 

 that a new moon and a change of weather mil happen together now 

 and then." To this the reply is that it is quite likely, for the moon 

 usually, in the course of each week, either crosses the equator or 

 arrives at one of the stitial colures. 



And those who have made atmosplieric changes a subject of 

 special observation, are compelled to admit that the theory of lunar 

 influence cannot be tabooed as unworthy of attention. In a number 

 of the Journal dts D^bals, published last summer, M. de Parville, in 

 an article on the temperature of the present year, says: — "A very 

 long series of observations has also shown that the moon, which 

 passes every month from one hemisphere to the other, influences the 

 direction of the great atmospheric currents. The changes in those 

 currents, in consequence of the prevailing moisture or di-yness, are 

 intimately connected with tho relative position for the time being 

 of the sun and moon." 



Admitting that the time of atmospheric changes, taking local 

 and climatic conditions into account, may be approximately known. 

 It remains to be seen how far the relative positions of the other 

 members of our solar system affect the character of the change ; 

 whether, for instance, the chemical rays of one planet, when sta- 

 tionary, or in conjunction or opposition of the sun, incline to heat, 

 and those of another to cold, is a legitimate matter of investigation, 

 always remembering that the wider the scope for surmise and as- 

 sumption, the more carefully must hastily-propounded theories be 

 tested by verified conclusions. To formulate into a system the effects 

 of solar, lunar, and planetary aspects and motions, requires long-ex- 

 tended and careful observation, but, on the other liand, it must not 

 be too hastily assumed that an error in detail proves the princijile 

 to be false — a sweeping condemnation which no logical mind should 

 accept. When mathematical or scientific demonstration cannot be 

 given off-hand, and when, consequently, so much dejicnds on the 

 even balance of the judicial faculties, scepticism is as dangerous to 

 the interests of the truth as credubtv. H. A. Blllev. 



i 



The Pki.nciple of the Veexieb, vide last week's K.vowledge, page 

 284, 11th line from bottom, 

 7 

 for " x= jTT + a fraction," Ac, 



8 

 read ". =35 -fa fraction," &c. j^^,^. g Campbell. 



SOMETHING ABOUT THE POTATO. 



HOW few of us ever give any thought to the food we eat, beyond 

 the fact of its being well or badly cooked. Very few know 

 that the potato for years past has, amongst other articles of food, 

 received the earnest attention of investigating chemists at homo 

 and abroad. A few of the facts resulting from their work during 

 the last few years, I now propose to try — without going into that 

 part of the researches which can only be of interest to the chemist, 

 sncli as giving the results of analyses, or the names of the various 

 alcohols which we are able to extract from the potato — and put before 

 3"ou as an interesting article. 



I daresaj- some, or rather most, of you have heard of potato spirit, 

 to obtain which, potatoes may be mashed either with mnll or sulphuric 

 acid. Mull, if anything, gives a trifle betterrcsult. In manufac- 

 turing this spirit we obtain an oil, called fusel oil, from which we 

 can extract nine different alcohols, as well as other organic sub- 

 stances, the names of which I will not trouble you with. Besides 

 the spirit and ether we obtain from potatoes, wc may soon advan- 

 tageously obtain pressed yeast. At present there is a little diflicnity 

 to be overcome in the working of the process, the diflicnity being 

 that the yield of spirit is less in proportion to the yield of yeast ; 

 but in a short time the chemists, who are working the solution of 

 this problem out, expect to overcome this obstacle. 



Another important produce manufactured from the potato is 

 potato starch, which, by the action of acid, is converted into 

 glucose-sugar, or syrup, which is chiefly made in America and Ger- 

 many, though we have, at the same time, some important works in 

 this country, and one quality is, from tlfc samples which I have seen, 

 for brewing and sweet manufacturing purposes, the purest. Owing to 

 the large amount of sulphuric acid present in some of the prepared 

 syrup in America, it has been found to have had an injurious effect 

 on the health of those people who have taken tho syrup, but this 

 acid should not be present in so large an amount as this. Some 

 samples I have tasted were perfectly free from it, and yon could 

 only taste the very sweet taste of glucose. On the other hand, other 

 samples have really been unbearable, owing to the large amount of 

 acid present— in one case, in the form of sulphurous acid, wliich 

 leaves the same taste in the mouth as a mouthful of burnt sulphur 

 would do, if inhaled. As glucose is one of the chief ingredients re- 

 quired for brewing, it is easily seen what an important substitute 

 for malt this must be to the brewers, though a few years ago 

 brewers would not acknowledge using it ! Its nse has since then 

 become more general, so brewers are not ashamed to own to using 

 it. Without going into detail, I will here give a general average 

 analysis of the potato : — 



Water Nitrogenous q;, Non-Nitrogenous eeUulose. 



substances. Substances. 



75-77 1-79 -16 20-56 -75 



A full analysis of the above, giving the names of all the non- 

 nitrogenous substances, &e., with their percentages, would take up 

 a good deal of space, without making the general reader any the 

 >viser than he was at the beginning. 



The next thing to bo considered is the general cultivation of the 

 potato, as made known to us by the chemists who have been study- 

 ing this branch of the tuber. Generally speaking, large seed pro- 

 duces more large potatoes than small seed. Most people might take 

 this for granted, without corroborating the sup])osition by numerous 

 experiments, as the chemist does, for the chemist mnst bring 

 forward positive results only to bear out his suppositions. 



The inlluenccs of the blossoms makes a great deal of difference in 

 the yield of the crop, as the following results show: — 208centrs. 

 191b. of tubers were obtained from plants from which the blossoms 

 had been removed, and only 181 centrs. 48 lb. from plants not so 

 treated. I do not think many readers of Knowleice would have 

 thought that the difference could have been so great. 



It has been found that the growth of sprouts on potatoes 

 depends on their nearness to the apex of the tuber ; if they aro 

 treated with water in sunlight, the growth increases forty or fifty 

 times, although this not the case in the dark. Absence of light is 

 necessarv for the growth of young tubers. 



Heat produces very beneficial results to the growing plant. On 

 this account too early planting is injurious, for potatoes require tho 

 same total heat to bring out the leaf buds; so, should the jilants bo 

 planted too soon, it would require, as experiment shows, perhaiis 

 forty days instead of fourteen to bring them to this stage, but it is 

 well', at the same time, to bear in mind the fact that if they are left 

 too late, the ground will become equally unsuitable. 



Potato rot is the next point to be considered, of which there are 

 three kinds— viz., dry, wet, and sweet rot. In the dry and wet rot 

 it has been found that the potatoes with the maximum starch resist 

 the disease most effectually. Potatoes grown on moist soils and 

 soils containing much organic matter are most liable to the disease. 

 The starch in diseased potatoes is yellow, but can be used for manti- 



