AlARCii 1, 18G5.J 



SCIENCE-GOSSIP. 



53 



which gradually becomes deeper, and a dirty, 

 inky-looking compound is ultimately produced. 

 When this has taken phice, chlorate of potash 

 in fine powder must be dropped into the hot 

 mixture very gradually imtil the black colour 

 disappears. This must be done cautiously, for 

 the action is so violent that much spurting is 

 occasioned, and the liquid being very corrosive 

 a tolerably capacious vessel should be used in 

 order to keep the splashes within reasonable 

 bounds, or sei'ious damage to the operator's 

 clothes may ensue. 



The nearly decolourized liquid must now 

 be diluted with a considerable quantity of 

 water, and the deposit allowed to svxbside, the 

 supernatant liquid poured off, and the pro- 

 cess of heating with sulphuric acid and addi- 

 tion of chlorate of potash repeated, until the 

 sul[)huric acid occasions no further blackening, 

 then the cleaning may be finished in the usual 

 way by washing. 



The chemistry of this process is thus ex- 

 plained : — When strong sulphuric acid is 

 brought in contact with organic matter it 

 abstracts the greater part of the water, setting 

 free the cai-bon in an imperfectly dissolved, 

 or, at least, finely divided state. Other changes 

 also take place of a somewhat complex nature. 

 The chlorate of potash being now added to 

 this mixture is immediately decomposed by 

 the sulphuric acid, supplying oxygen to the 

 carbon, with v/hich it forms carbonic acid gas, 

 which escapes with some free chlorine. Other 

 oxidizing agents may be used ; nitrate of 

 potash may be added in the same way as the 

 chlorate, or nitric acid itself may be used, but 

 they are all inferior to the chlorate. This 

 process was published some few years back, 

 and has been found by experience to be the 

 most efficacious method of operating on guano 

 for Biatomacece. The operator requires no 

 small share of patience in working on guanos, 

 for it sometimes happens that some samples 

 yield none, or so few as to be scarcely worth 

 the trouble of cleaning. When, however, the 

 yield is good, the experimenter is well repaid 

 for his time and materials. 



In consequence of guano being so largely com- 

 posed of organic matter it is well to work on a 

 tolerably large quantity, say a pound, or, at all 

 events, not less than four ounces. The writer 

 has found the Peruvian and Californian to 

 3vield a very rich variety of these minute 

 objects. It may be as well to mention that 

 the above processes may be well applied to 

 the cleaning of the siliceous cases of our native 

 species. The matters containing them should 

 be allowed to dry before being subjected to 

 the action of the acids. 



It is scarcely necessary to add a caution as 

 to the corrosive nature of the acids here em- 

 ployed; the operations should also take place 

 under a chimney or in a well-ventilated 

 apartment. In case of accident apply plenty 

 of cold water, then any alkali at hand, chulk, 

 or whiteninsr. 



LEAF TEACHINGS, 

 By W. Wallace Fyfe. 



OERSTED observes, in his "Soul of 

 Nal.ure," that organic beings constitute 

 the elementary, and inorganic the higher 

 geometry of nature ; and, although we meet 

 with many regular mathematical forms in the 

 leaves of plants, whether triangulai', poly- 

 gonal, cylindrical, spherical, or elliptical (for in 

 what may be scientifically termed leaves we 

 have all these), nevertheless, in the shapes of 

 leaves and the flow of their venation we 

 have seldom figures that are severely exact ; 

 yet, for all that, every atom of the most 

 waving lines and outlines is capable of being 

 reduced to a regular curve. It was Goethe 

 who defined all the appendages of the plant 

 as leaves* — transformed leaves. We do not go 

 so far as the German poet and philosopher, but 

 deem it sufficient to recognise the truth that 

 all are modelled after the leaf. The form of the 

 leaf, therefore, becomes a generic principle in 

 structural botany. The structure of a leaf 

 is founded on what have been termed archi- 

 tectural principles ; but in truth it is archi- 

 tectural principles that have been derived 

 from it, since Sir Joseph Paxton has acknow- 

 ledged that to the ribbing so peculiarly 

 adapted for bearing up the broad floating leaf 

 of the vast Victoria Regia and its massive 

 inflorescence, he was mainly indebted for the 

 idea of his palace of glass, which has so 

 wonderfully resisted, in its fairy-like frailty of 

 appearance, the storms of time. If we are 

 entitled, with Goethe, to extend this principle 

 of structure from the leaf to the tree, we 

 shall find that to it also Smeaton was in- 

 debted for the design of the Eddystone Light- 

 house — a structure calculated to sustain weight 

 and resist pressure — since he derived it from 

 the bole of a tree. The elements of plant 

 structure are found, however, in the cell — • 

 the lower forms of plants being simply cells 

 separate and independent ; the higher forms, 



* Liniifieus had previously affirmed the leaf to be 

 the type of all the floral org-ans. Goethe's T'ersnch 

 die Metufdoi-phose ckr Fj'lanzeii zu erkJdren was 

 published in 1?90, 



