124 



KNOWLEDGE 



[June 1, 1899. 



therefore not unreasonable to conclude that the earthquake 

 was due to a double slip along a continuation of this fault 

 to the north-west. 



Whether this be the case or no is not, perhaps, a matter 

 of much importance. The noteworthy fact is that the 

 earthqualce-fault is roughly parallel to the axis of the well- 

 known Woolhope anticlinal, and not far from its south- 

 west boundary ; that it probably forms part of the series 

 of movements which have given rise to the structure of 

 this interesting district. 



It is not possible to determine the position of the two 

 foci with very great accuracy, but, judging from the form 

 of the isoseismal 8, the course of the hyperbolic band, and 

 the duration of the two series of vibrations and of the 

 interval between them, we cannot be far wrong in 

 estimating the length of the north-west focus at about 

 eight miles, with its centre beneath a point about three 

 miles south-east of Hereford ; and the length of the south- 

 east focus at about six miles, with its centre beneath a 

 point two or three miles north-east of Eoss. Between the 

 two foci there would thus be an undisturbed portion of 

 the fault-service about two miles in length. With regard 

 to the depth of the two foci, in this, as in every other 

 earthquake, nothing definite can be stated. 



One of the most interesting problems in connection 

 with the earthquake is the origin of the double focus : and 

 I venture to suggest the following as the solution. The 

 earthquake fault, as we have seen, runs north-west and 

 south-east. In the neighbourhood of the north-west focus, 

 its hade is to the north-east. The hade may change 

 to the south-west near the south-east focus and the May 

 Hill anticlinal, but this is immaterial to the explanation. 

 If we were to make a section of the north-east rock-mass 

 by a north-west and south-east vertical plane, I imagine 

 that beds originally horizontal would now be curved, so 

 that there would be an anticline where the section passes 

 through the Silurian Woolhope anticlinal, and a syncline 

 through the newer rocks to the south-east, opposite the 

 May Hill anticlinal. Between these folds there would be 

 a region (corresponding to that between the two foci) where 

 there is little or no vertical displacement. Now if the crust- 

 movements which caused the earthquake were such as to 

 accentuate this structure, there would be two slips — one 

 at the north-west focus, that would be partly upwards and 

 partly to the south-west (at least relatively to the rock- 

 mass on the opposite side of the fault), and the other at 

 the south-east focus, partly downwards and partly to the 

 north-east, while in the region between them there would 

 be no perceptible movement. 



It should be mentioned, however, that there were several 

 slight shocks — nine before and three after — the principal 

 earthquake, and that three of these appear to have origi- 

 nated in the intermediate region. It is difficult, owing to 

 the scarcity of observations, to locate the foci of some of 

 the other shocks ; but the majority of them seem to have 

 been connected with the south-east focus. Possibly this 

 is the reason why, in the principal earthquake, the vibra- 

 tions from the north-west focus were so much more severe 

 than those which proceeded from the other. 



THE DISCOLORATION OF CUT APPLES. 



By G. Clarke Nuttall, b.sc. 



THE processes in the evolution of an apple tart 

 present no difficulty to the most ordinary practical 

 cook, though to the average learned scientist the 

 gradual building up of this eminently English dish 

 is apt to be a matter of some wonder. He wonders 

 because he realizes his ignorance of culmary details and 



his helplessness if he be confronted with them practically ; 

 while, in her, familiarity ha,s bred contempt to such an 

 extent that she does not realize the limits of her know- 

 ledge, and can see no one thing in all the various details 

 that calls for wonder or remark. And yet she might well 

 do so, for at a certain stage that happens which has both 

 puzzled and excited the interest of botanist and chemist, 

 though she passes it by ignorant, and yet not knowing 

 her ignorance. 



As the apples lie piled up in slices in the dish waiting 

 for their covering of paste, every housewife knows that 

 they have a tendency to turn from their normal white to 

 first a reddish, and then a brown colour, and that if they 

 are left standing in the air uncovered for very long they 

 become an unpleasant dirty-brown hue which is distinctly 

 unappetising. So unappetising is the colour that if part 

 of an apple be eaten and the rest put aside for a short time, 

 a fastidious eater will throw it away rather than finish it, 

 even though the flavour is quite unimpaired. This redden- 

 ing of the flesh of apples cut and exposed to the air is one 

 of those phenomena whose everyday occurrence has taken 

 away curiosity, and ranged most people on the side of that 

 cook who saw nothing in it to wonder at as " they always 

 went like that ! " And yet this change of colour is a 

 Gordian knot which many have attempted in vain to untie, 

 and which even yet is not altogether free. 



Why should apples, pears, and, to a less extent, potatoes, 

 thus change colour in the air, and only make this change 

 when they are in their raw uncooked state '? What is the 

 true inwardness underlying this external symptom ? To 

 simply say it is due to a process of oxidation does not 

 convey much definite knowledge to the inquirer, and, 

 indeed, it is only during the past few years that much 

 progress has been made in understanding better the reason 

 of this change in colour. 



The latest and most thorough explanation is one lately 

 put forward by a chemist named Lindet, and it is an ex- 

 planation of considerable interest. Within the cells of the 

 tissues which make up the fleshy part of the apple — the 

 part that is eaten — there is produced in their jelly-like 

 contents a certain product to which the name malase or 

 laccase has been variously given (malase will probably be 

 the name finally used, as laccase has already been adopted 

 for another product) ; and this product belongs to a curious 

 class of substances known as enzymes. Enzymes have only 

 been discussed seriously of late years, and even up to quite 

 lately much doubt has been expressed as to what their 

 properties are, and even indeed if they had any real exis- 

 tence or not ; however, that point is now practically settled, 

 and, in fact, they have been isolated and examined. 



Now, an enzyme is a production of the activity of the cell 

 which has the unique power of influencing other substances 

 in its neighbourhood, and yet remaining unaltered in any 

 way itself. It can exert influence without, apparently, 

 being affected by doing so. Its own constitution is stable, 

 but it possesses power to act, even at a distance, on certain 

 of its surroundings, and produce great effects on the con- 

 stitution of other matter, in some way not yet thoroughly 

 comprehended. It will be seen at once that this is a very 

 different thing from ordinary chemical action. In chemical 

 action one substance acts on another by effecting some 

 exchange, or producing some re-arrangement of the atoms 

 comprising both substances. In combining with another 

 it must itself be changed according to some definite law, 

 and only through that change can chemical action be 

 effected. Moreover, there is a definite limit to chemical 

 action, and when once the new combination is brought 

 about, and a stable equilibrium ensured, then there is an 

 end of the matter until new substances come into play. 



