2G8 



HAHDWICKE'S SCIENCE-GOSSIP. 



however fine the crack may be, the fragments in 

 separation generally exhibit the striation on both 

 surfaces of the interior, and the lines run in 

 precisely the same direction on all the surfaces 

 marked ; thus showing the structure to prevail 

 through the entire mass. 



The appearances which have been above described 

 seem to me to be inconsistent with the idea of their 

 having been produced by the rubbing of one block 

 against another under pressure. The effect of such 

 rubbing of two pieces of marl would, I believe, be 

 to produce a smooth polished surface, not a rough 

 striated one, such as I have described ; moreover, 

 had the effect been due to any such cause, the 

 markings would occur in every possible direction, 

 without any uniformity ; whereas in the case under 

 consideration the markings for the most part lie in 

 the direction of the stratum or deposit. 



Without commenting on the various opinions 

 held by geologists on the subject, I may briefly 

 state that my own opinion at present is that the 

 ridges in the striation are the exposed edges of thin 

 layers of siliceous matter, or matter at least harder 

 than pure chalk ; and that they represent successive 

 deposits of this harder matter. Wherever a block 

 of the marl has been cracked so as to admit the 

 entrance of the atmosphere, a slow weathering has 

 taken place, which has resulted in the removal more 

 or less of the softer parts of the original deposit, 

 leaving the harder or siliceous ones exposed as 

 ridges. 



To produce this effect, the weathering must have 

 been very gentle in its action, and continued over 

 a long period of time. EuU exposure of the surface 

 to wind and'rain wouldihave produced no such effect ; 

 hard land soft parts would have alike yielded to the 

 action, and no distinction in the shape of striation 

 would have been observable. 



The per-centage of siliceous and earthy matter in 

 the marl in question is very large, as may easily be 

 ascertained by dissolution of a fragment in dilute 

 muriatic acid. The residue is dark, and does not 

 become perfectly white by ignition. 



C. J, MULLER. 



SOME KEMARKS ON TEA AND SLOE 

 LEAVES. 



y^ LTEEOUGH there does not exist the same 

 -'--*- temptation to adulterate tea now there was 

 in the olden times, when its cost was even more 

 than as many shillings as what it is pence per 

 pound, yet the abominable practice, rather than 

 having been diminished in the like ratio with the 

 temptation, has, if anything, only increased.* My 



* This has reference to the use of tea adulterants generally, 

 and not to the Sloe in particular. 



object, mainly, is to illustrate and show by contrast 

 the differences which exist, structurally, between 

 the leaf of the Tea and that of — what at one time 

 was its much-used substitute — the Sloe. In doing 

 this it will be perceived that I have given pro. 

 minence to the serratures of the margins, and their 

 lateral venations, rather than to the general appear- 

 ance of each as a whole. This, I have done de- 

 signedly, since it is in these particulars more than 

 in any other that the physiological points of dif- 

 ference reside. In what these differences consist 

 will readily be seen by reference to the accompany- 

 ing figures. Beginning with their serratures, then, it 



Fig. 1/2. Sloe Leaf {Frunug spinosa). 



Avill be detected that those on the margin of the 

 tea-leaf only take their rise from about a quarter 

 to half an inch above its base, whilst in the leaf of 

 the Sloe they are continuous from base to apex. I 

 might observe further, too, that they vary in respect 

 of their apices, which in the Tea is more or less 

 visibly emarginate, according to variety, a par- 

 ticular that renders it out of all correspondence, 

 botanically speaking, to the apex of the Sloe, 

 which is acute. The other difference of character 

 already alluded to, but undetailed by me, is that of 

 their venations. These when viewed will, in that 

 of the Tea, be noticed but to proceed from the 

 midrib or central stem, to only within a short 

 distance of the leaf's edge, in a recurvate manner. 

 In the Sloe they are, on the other hand, in direct 

 contact with the margin. Eor other and further 

 differences take the leaves themselves. A super- 

 ficial examination will soon discover to the botanic 

 eye, a varying lamina, which in the case of the Tea 

 will be found rather thick and somewhat coriaceous, 

 in which the veinings are immersed, while in that 

 of the Sloe it is comparatively thin and tender, with 

 veining prominent. Continuing the examination 

 further still, but microscopically, the stomata of 



