February 1, 1892.] 



KNOWLEDGE 



25 



severed from the capsule itself ; he will observe the double 

 peristome (i.p. and o.;).),the outer teeth consisting of a pro- 

 longation of the outer coat of the capsule, the inner teeth 

 arising ir. like manner from the wall of the inner sack or 

 spore case, or sporangium (sp.) ; he will observe an interspace 

 between these two sacks filled with cellular tissue ; he will 

 observe in the interior of the sporangium the cells which 

 become spores with the maturity of the growth ; and in 

 the middle of the diagram he will notice the columella or 

 column. At the base of the capsule he will see the region 

 {lip.) which, when swollen or enlarged, gives rise to the 

 apophyse. All these parts are subject to a great range of 

 variation, but this diagram may nevertheless, I hope, prove 

 of some assistance to those beginning the study. 



The object served by the complicated structure of the 

 peristome is not, perhaps, very certain, but it seems to be 

 intended to secure the retention or exclusion of the spores 

 fi'om the spore sac in such conditions of the atmosphere 

 as will best conduce to their germination. In the 

 Gymnostomous Mosses {i.e., those without peristome) it is 

 observed that the spores sometimes germinate within the 

 capsule, an event which is probably adverse to the 

 prospects of the race. The following table will illustrate, 

 in a few cases selected as illustrations, the different 

 behaviour of the teeth of the peristome under different 

 hygrometric conditions, and suggests what is the probable 

 advantage in each case ; — 



TABLE D. 



The motion of the teeth of the peristome appears to be 

 due to the action of the annulus, a ring of specialized 

 cells which surrounds the mouth of the capsule at the 

 base of the teeth : jind the opposite ways iu which these 

 cells act in the same condition of moisture in different 

 genera is a remarkable circumstance. 



To anyone who studies the subject, the immense variety 

 as well as beauty of the peristomes of Mosses becomes very 

 impressive. If the sole end be the protection and extrusion 

 of the spores in the proper weather respectively, why is 

 there this infinite wealth and variety of form and of 

 colour? The question can be asked, but hardly can be 

 answered : and the mind of the beholder is left, as it so 

 often is when contemplating the richness of Nature, in a 

 state of admiration and wonder and ignorance. " Rerum 

 natm'a tota est uusquam magis quam in minimis." 

 {To he continued.) 



THE CHEMICAL ELEMENT CARBON. 



By Vaughax Coknish, B.Sc, F.C.S. 



THE older conception of a chemical element was that 

 of a property, or plexus of properties, which being 

 CO mmon to several substances was regarded as a 

 piinrijite existing in all those substances. In some 

 of these old principles we can recognize the present 

 chemical elements. But whereas we now think of the 



elements as the undecomposed residues of natural sub- 

 stances and as being forms of ponderable matter 

 essentially uncreatable and indestructible, the earlier 

 conception of a chemical principle was that of a constant 

 property possessed by certain forms of matter, c.ij., the 

 combustibility which is a property common to all sub- 

 stances of animal and vegetable growth. It is the depen- 

 dence of certain properties on the presence of certain 

 kuads of material substance which aids us in many eases 

 to connect the older chemistry with that of the present 

 time, by identifying some of the so-called principles of the 

 seventeenth century with the corresponding elements of the 

 nineteenth century chemists. 



A short history of the study of Carbon will serve to show 

 the gradual evolution of certain important modern ideas 

 with regard to chemical elements. 



^Yhen vegetable or animal materials are heated with a 

 limited access of air the result is that they are charred. 

 Materials differing in almost every respect, except in their 

 being formed in the processes of animal or plant Ufe, 

 agree in this — that when treated as above described they 

 yield a char. The word curlm, formed from the same root, 

 appears to have been used in the Augustan age in the same 

 sense, namely, to designate the char left by the partial 

 burning of animal and vegetable bodies. It was usually 

 applied to the char obtained from wood or wood charcoal. 

 In the more modern use of the Latin tongue cario 

 generally means coal, the vegetable origin of which is 

 readily recognized. 



The first important generalization in the history of 

 chemistry is that contained iu the theory of Phlogiston, 

 which retained its hold upon the minds of chemists till the 

 later years of the eighteenth centiu-y. The merit of this 

 system lay in the fact that the various phenomena of 

 oxidation were for the first time grouped together and 

 referred to the same agency. 



The change of properties undergone by metals on 

 calcination was a favourite subject of study with the 

 phlogistic chemists. An equal share of their attention 

 was devoted to the means of restoring to calxes (or oxides) 

 the metallic properties. The phlogistic chemists recog- 

 nized that the process of calcination of metals was 

 essentially a process of burning. Now the char or 

 substance left by the partial burning of animal and 

 vegetable bodies constitutes the most generally applicable 

 material for the preparation of the metals from their ores, 

 or from the calxes. The calx or ore is mixed with char- 

 coal, or with the analogous material coal, and these being 

 heated together, the charcoal or coal is consumed, to all 

 appearance ceases to exist, and a metal is produced from 

 the calx. 



It is to be observed that these changes only take place 

 at a high temperatm-e, and that the materials must therefore 

 be heated. Now the primitive method of heating is to 

 kindle a mass of vegetable matter such as wood, burning 

 the material with a free supply of air. It was, however, 

 found that for metallurgical operations it was more 

 advantageous to employ the prepared material charcoal, 

 instead of the crude material wood. In metallurgical 

 operations the charcoal (or the analogous material coal) 

 plays two parts, each of which is essential to the reduction 

 of the ore or calx. The first of these functions is the 

 production of a high temperature, the second that of acting 

 on the heated ore so as to form a metallic substance. 

 The charcoal employed as fuel has undergone combustion, 

 and the charcoal mixed with the ore has apparently 

 imparted to the ore the power of burning, that is to say, 

 has formed from it a metal which is a material capable of 

 btu'ning. Coal, coke, wood charcoal, animal charcoal, 



