July 1, 1889.] 



♦ KNOV\rLEDGE ♦ 



18B 



Spain. In fact, in the three latter localities, extensive 

 masses of mineralised phosphate known as " phosphoiite " 

 occur. 



Sometimes phosphates are found in a highly mineralised 

 condition in well-defined crystals, which have evidently been 

 deposited from solution in the rocks where they are found. 

 Such phosphates are found in old rocks in Canada and 

 Norway, also in Spain, and are known as apatites; they 

 consist of calcium fiuoride and pho.sphate, and sometimes, as 

 is the case with Norwegian apatite, of the chloride as well. 

 The crystals sometimes are of considerable size : some very 

 big ones from Canada were exhibited in the Indian and 

 Colonial Exhibition, and looked like hexagonal pillars arti- 

 ficially shaped. 



Other sources of phosphate for the farmer are the guano 

 deposits. They mainly originate from the excretory deposits 

 of sea birds ; when fresh or in protected places the deposits 

 contain much organic matter, and consequently nitrogen as 

 well as phosphates, but in old deposits or in places exposed 

 to severe atmospheric influences, heavy rains, heat, <tc., the 

 organic matter has disappeared and only inorganic matter 

 remains, which in course of time becomes washed into and 

 mixed up with the rock. Nitrogenous guanos are found on 

 the islands near to and on the coast of Peru, in Patagonia, 

 and the Falkland Islands in South America, and on the 

 islands of Ichaboe and Ascension in Africa. Guanos con- 

 taining phosphates but no nitrogen are found on many of 

 the West Indian islands, in Mexico, on some of the islands 

 in the South Pacific Ocean ; also on the Kuria-Muria 

 islands in the Arabian Sea ; in New Guinea, Australia, 

 &c., &c. In some localities the guano is found deposited 

 along with other animal remains, and bones, teeth, and shells 

 ai-e found mixed up with it. Cura(5"ao and Barbadoes 

 guanos are of this type. 



Coprolites consist of nodular, spherical, and irregular 

 lumps of phosphate, which are dug out of the earth 

 in Cambridgeshire, Buckinghamshire, Bedfordshire, and 

 Suffolk, in England. They are also found in the north of 

 France, in Russia, and in Austria. They are supposed to 

 be the fossilised excreta of huge extinct lizard-like animals, 

 but in the majority of cases there is little or no evidence to 

 support this suppo.sition. 



All the natural phosphates that have been here considered 

 are insoluble, or practically so, in water ; they cannot, 

 therefore, in the raw state be easily distributed in the soil 

 BO as to be accessible and useful to the plants. Fortunately, 

 however, simple treatment with sulphuric acid (oil of 

 vitriol) converts them into a soluble form of phosphate and 

 gypsum; such mixtures contain all theother fixed constituents 

 of the original raw phosphate, and are known as superphos- 

 phates. The phosphate in superphosphates is mostly soluble, 

 and, when applied to land, is washed into the soil by rain, 

 and becomes well distributed throughout so as to be i-eadily 

 accessible to the plant roots ; in contact with various soil 

 constituents it, however, soon again assumes an insoluble 

 form, and is, therefore, not washed away like nitrates. 

 Before concluding, a word or two must bo added about a 

 source of jihosphates which cannot be considered of animal 

 origin. Until the year 1879 iron obtained from ores 

 containing phosphates even in very small quantities, as 

 a great many iron-ores do, could not be used for the manu- 

 facture of steel because the metal retained the phosphorus, 

 which contributed undesirable and deteriorating properties 

 to (ho steel. In the year 1879, however, Messrs. S. G. 

 Thomas and P. G. Gilchrist made known to the world their 

 discovery of lining the vessel in which the iron is melted to 

 convert it into steel with lime, or a mixture containing much 

 lime, and also adding lime to the molten metal. This pro- 

 duces wonderful changes, the lime combines with the phos- 



phorus to form phosphate, which then separates from the 

 mass of molten metal and floats on the top along with 

 other impurities, forming what is known as " basic slag." 

 By this discovery much material, which had hitherto been 

 useless for the purpose, could be employed for the manufac- 

 ture of that extremely valuable material, steel, the quality 

 of which was greatly improved bj' the removal of the phos- 

 phorus. What is more, this phosphorus, which was formerly 

 not only absolutely useless but also a nuisance, is converted 

 in this " basic " method of making steel into a valuable 

 source of phosphate for the supply of that all-important 

 plant constituent to our crops. 



OUR MICROSCOPIC FOES. 



By a. Winkelried Williams. 



F all the foes that are waging war against 

 mankind the most dangerous and deadly are 

 minute organisms belonging to the lowest 

 orders of plant-life, and invisible to our 

 naked eye. An immense number of these 

 always surround us, and are ready to make 

 an attack should they find a weak point in 

 our defences. 



Their presence in the air may be readily demonstrated by 

 exposing some material upon which they can feed, and 

 watching the result. The simplest method is to boil a potato, 

 cut it in half, and immediately place one half under a bell 

 glass purified by being washed in an antiseptic solution such 

 as corrosive sublimate. Expose the second half to the open 

 air for a short time, and jihice it also under a glass. Let 

 them remain for a few days, and then examine. If the first 

 half has been placed rapidly enough under the glass, we shall 

 find it unaltered. On the second half, however, we shall see 

 a number of small but growing spots, which will probably 

 vary much in colour. These consist of colonies made up by 

 immense numbers of the most minute plants, i.e., bacteria, 

 and also of higher fungi. Certain species of the bacteria 

 constitute our dreaded foes. 



Bacteria are non-nucleated unicellular plants, which may 

 be roughly classed into two divisions according to their shape, 

 the circular forms being called micrococci, the elongated 

 forms bacilli. In size they are most minute, being only 

 visible under the highest jiowers of the microscope. ]\Iam- 

 are provided with cilia, by the lashing of which they are 

 capable of independent movement. They arc composed of 

 a peculiarly resistant protoplasm, which is condensed at the 

 surface, so that by the action of certain caustics they can be 

 separated from many tissues on which they may be lying, 

 the caustics destroying the.'^e tissues. 



Bacteria have enormous power of reproduction, which is 

 accomplished by division of the cells and fission. Many 

 also form globular spores by a condensation of their proto- 

 plasm. The spores have a much higher power of resistance 

 than the bacteria themselves, and may, under unfavoui-able 

 circumstances, bo quiescent while awaiting better times to 

 take on full development. 



Their habitat is almost everywhere. In water bacteria 

 exist in great numbers ; they are even found in springs 

 at their sources. This indicates their presence in the soil, 

 where they ,aie found in great numbers. We have already 

 seen that they exist in the air ; but, being, for their size, 

 heavy bodies, they are invariably attached to less dense 

 particles of dust. Out at sea we find the air free from 

 bateria, although in the water they abound. The higher 

 we ascend the fewer we find. In (owns the air teems with 

 them, in the country but few exist. In (he hcal(hy livirg 



