114 



KNOWLEDGE & SCIENTIFIC NEWS. 



[June, 1904. 



arriving at the bottom, which it is very apt to do in 

 gusty weather. 



By the courtesy of the Mana<:;ement of the Crystal 

 Palace, the magnificent grounds of that institution have 

 been placed at my disposal, and a most suitable spot was 

 soon found beside the Intermediate Lake. Mere I have 

 had a larsje staging erected, of which the accompanying 

 photographs will give a good idea. 



Mr. C. J. Pilomfield, the well-known architect, very 

 kindly undertook to superintend the details of construc- 

 tion. This staging is of wood, the upper end beinj,' some 

 30 feet abo\-e the level of the lake. '1 he incline is one in 

 two, the lower end forming a curve of '10 feet radius. 

 The "take off" is on an upward incline of one in ten, 

 the lowest portion of the track beint; about ten feet from 

 the outer end, which is six feet above the water level. 



The rails are composed of solid slabs of oak securely 

 bolted lo the structure, and projected inwards so as to 

 allow of runners enijaging on their under sides as well as 

 on the upper. They have a gauge of 2 ft. f> in. These 

 are carefully smoothed and greased to minimise friction. 

 The flying apparatus consists of a boat, flat-bottomed, 

 and with a considerably rockered stem, about 20 feet 

 long over all, by 2 ft. 6 in. beam. From the sides of this 

 project runners of oak to slide on the rails, and also some 

 projections which are to engage the under sides of the 

 rails in the event of the wind lifting the wings on one 

 side, and thus prevent the machine being overturned or 

 lifted upwards off the track. 



The rate of descent is found to be 50 feet per second 

 near the bottom, but this speed is, of course, diminished 

 slightly during the upward incline before the boat leaves 

 the track. An electric chronograph is to be fitted so that 

 the speed can be measured over various sections of the 

 track. The track is only just completed, and the proper 

 man-carrying boat is still in hand. 



The photographs show a skeleton pattern boat which 

 was constructed to better get at the most suitable 

 dimensions and shape. This, as may be seen, was 

 fitted with two rectangular aeroplanes, each 12 feet by 

 5 ft. 6 ins., so that the area of this model is 132 square 

 feet. Later on it is proposed to apply other shapes and 

 forms of aeroplane to compare various patterns, and tails 

 of different designs will also be tried. 



I propose shortly to start making regular trials and 

 shall hope to be able to give full accounts of these in the 

 next number of " Knowledge & Scientific News." 



Mr. J. Semenoy (see Journal dc Physique, Feb., 1904) causes 

 electric sparks to jump between two gas flames or a flame and 

 a metallic electrode, or else between two metallic electrodes 

 separated by a small gas flame. By this arrangement the 

 glow is eliminated, so as to enable the spark proper to be 

 examined separately. In fact the metallic vapours constituting 

 the glow are blown aw.ay by the gas stream of the flame. 

 The image of the spark is projected by means of a con- 

 vergent lense on the vertical slit of a direct-vision spectro- 

 scope, the axis of which is perpendicular to the plane of the 

 spark gap. 



Semenov's experiments go to show that dirtric currents in 

 gases are a molecular phenomenon ; this would be in accord with 

 Professor Bouty's researches on the dielectric cohesion of 

 gases, which is also a molecular property. 



Such currents are attended l>y the dissociation and projec- 

 tion of matter, the paths of which are in each point of the 

 spark orientated in a plane perpendicular to the line of current. 

 On account of the projection of matter taking place round the 

 spark, a vacuum must be produced along the spark, the 

 atmospheric pressure throwing into this vacuum the air and 

 metallic vapour surrounding the electrode ; this is obviously 

 one of the causes of the transport of matter taking place from 

 one pole to the other. — A. G. 



The Development of 

 Parasitism. 



r.y J. Re'ixolos Grei:n, Sc.H., I'.K.S. 



The early ancestors of all plants now existing are 

 generally held to have been aquatic organisms of fairly 

 simple type, and of not very complex structure. Without 

 going back to the extremely simple protoplasmic entity, 

 whose nature cannot be said with certainty to have been 

 vegetable rather than animal, we must admit the exis- 

 tence of a I'ace of plants, each of which was capable 

 of living for and by itself, of carrying on all the functions 

 of nutrition, and of reproducing itself. The power of 

 nourishing itself involved a further power; it must have 

 been able, under the infiuence of the rays of the sun, to 

 construct or.Ljanic food material from the inorganic simple 

 compounds furnished to it by its enviromnent. The 

 possession of this power was one of the earliest acquired 

 marks of distinction between the animal and vegetable 

 organisms, for though traces of it may be found in the 

 former, they are but traces ; and it is uncertain how far 

 they actually pertain to the animal world. The vege- 

 table organisms on the other hand, bavin"; once acquired 

 the power, have retained and developed it till it is now 

 recognised as their special and distinctive feature. 



This peculiar property of constructing organic material 

 from inorganic, on which all physical life depends, is 

 associated with the presence in the vegetable organism 

 of a peculiar green colourin,<i matter, known as chloro- 

 phyll. The pigment is in nearly all cases found associated 

 with peculiar differentiated portions of the living sub- 

 stance, known as plastids, which, though commonly small 

 ovoid bodies lying in the general protoplasm of the 

 organisms, may in the more lowly forms assume curious 

 shapes. The power of food construction from inorganic 

 materials and the presence of these chUiraplasiids go 

 together, and the possession of what is often called 

 this chlorophyll apparatus is the distinguishing feature of 

 most plants. 



Endowed with this apparatus, exposed to the rays of 

 the sun, supplied with such simple inorganic substances 

 as the carbon dioxide of the air, the water and the 

 nitrates, sulpliates, and phosphates of the soil, the plant 

 can fight its own battles and reproduce its race. 



In studying the vast field of vegetation that the face 

 of the earth presents us with, however, we come across 

 many types which are not nourished in this way, which 

 have no power of food-construction, and which can only 

 live, animal fashion, on organic materials ready made for 

 them. 



Looking more closely into the habits of such plants, 

 we can distinguish between two classes of them, one 

 thriving on dead, decaying organic matter, the other 

 preying upon living organisms. 



The latter form the great group of parasites, a degraded 

 class which thrives by robbing other organisms of the 

 food they fiave acquired, and by taking from them 

 their own vital fluids, causing malnutrition and death. 



The study of parasitism as seen in the \egetable king- 

 dom illustrates very fully the law which is so well 

 illustrated in the processes of the evolution of the races 

 of both animals and plants, that disuse is followed by 

 atrophy. Whether the parasitic plant lives at the ex- 

 pense of another plant or whether it attacks an animal 

 organism, the result is the same — the disappearance of its 



