Staple Dietary Ingredients Secured | My Web Site Page 017 Chapter 01 Page 01

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The first care of the male stickleback, when he has acquired his courting suit, is to build a suitable home for his future wives and children. So he picks up stems of grass and water-weeds with his mouth, and weaves them deftly into a compact nest as perfect as a bird's, though some what different in shape and pattern, it rather resembles a barrel, open at both ends, as though the bottom were knocked out: this form is rendered necessary because the eggs, when laid, have to be constantly aerated by passing a current of water through the nest as I shall describe hereafter. No. 1 shows us such a nest when completed, with the female stickleback loitering about undecided as to whether or not she shall plunge and enter it. You will observe that the fabric is woven round a fixed support of some waving water-weeds; but the cunning little architect does not trust in this matter to his textile skill alone; he cements the straws and other materials together with a gummy mortar of mucous threads secreted for the purpose by his internal organs.

~Filtration.~--Solutions are best filtered hot whenever the assay allows of this being so done. The precipitate should be allowed to settle, and the clear liquid decanted on the filter with the aid of a glass rod if necessary. The filter-paper must not be too large, but at the same time it must not be overloaded with the precipitate. There should be ample room for washing. For general use three sizes of filter-paper are sufficient. Common quick filtering-paper (English) is best for most work in assaying. The specially prepared paper (Swedish or Rhenish) is used for collecting those precipitates which have to be weighed. The papers are folded as shown in fig. 16, and should not project above the funnel. The filter-paper works better if damped with hot water. In special cases filtering is hastened by means of an air-pump. The apparatus used consists of a water-jet (fig. 17), which is connected with the tap, as also with a bottle fitted as shown in fig. 18. The pump draws the air out from the bottle, and atmospheric pressure forces the liquid through the filter-paper. The bottom of the funnel is provided with a platinum cone, which supports the filter-paper, and prevents its breaking. The pump is only used in exceptional cases; nearly all the filtrations required by the assayer can be made without it. The usual methods of supporting the funnel during filtration are shown in fig. 19. Where the filtrate is not wanted, pickle bottles make convenient supports. After the precipitate has been thrown on the filter, it is washed. In washing, several washings with a small quantity of water are more effective than a few with a larger quantity of that fluid. The upper edge of the filter-paper is specially liable to escape complete washing. Excessive washing must be avoided; the point at which the washing is complete is found by collecting a little of the filtrate and testing it. The precipitate is removed from the filter-paper for further treatment by opening out the paper and by washing the precipitate with a jet of water from a wash-bottle into a beaker, or back through the funnel into the flask. In some cases, when the precipitate has to be dissolved in anything in which it is readily soluble, solution is effected in the filter itself allowing the liquid to run through as it is formed.

Whether the universe is really a paying concern, or whether it is an inflated bubble that must burst sooner or later, this is another matter. If people were to demand cash payment in irrefragable certainty for everything that they have taken hitherto as paper money on the credit of the bank of public opinion, is there money enough behind it all to stand so great a drain even on so great a reserve? Probably there is not, but happily there can be no such panic, for even though the cultured classes may do so, the uncultured are too dull to have brains enough to commit such stupendous folly. It takes a long course of academic training to educate a man up to the standard which he must reach before he can entertain such questions seriously, and by a merciful dispensation of Providence, university training is almost as costly as it is unprofitable. The majority will thus be always unable to afford it, and will base their opinions on mother wit and current opinion rather than on demonstration.

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