48: 



NA TURE 



[March 20, 1884 



level, for then very rapid pedalling would be necessary to 

 maintain even a moderate speed. To obtain the advan- 

 tage of high wheels or high gearing on the level and at 

 the same time low wheels or low gearing on the hills, 

 some highly ingenious devices are employed. On the 

 table is a well-known one of these, the " Crypto-dynamic," 

 which by a simple movement changes the relative speed 

 of wheel and treadle Time will not permit me to de- 

 scribe the details of this arrangement, but it contains an 

 epicyclic gear which is or is not in action according as 

 the rider desires power or speed. There are several 

 other devices having the same object, some depending on 

 an epicyclic gear in a pulley, others on the use of two 

 chains, only one of which is active at a time. These 

 arrangements have the further advantage of enabling the 

 rider to disconnect the treadles from the wheels whenever 

 he pleases. 



Tricycles on which two, three, or a whole family can go 

 out for a ride together, involve few new principles, and I 

 shall not for this reason have a word to say about them. 



There remains one machine forming a class by itself, 

 more distinct from all others than they are from one 

 another. It is not a bicycle in the ordinary sense of the 

 word ; it is not a tricycle, for it has only two wheels. 

 This machine is, from a scientific and therefore fiom 

 your point of view, more to be admired than any other. 

 It is called, after its inventor, the " Otto." The Olto 

 bicycle and the Otto gas-engine will be lasting memo- 

 rials to the ingenuity of the brothers who invented 

 them. 



No machine appears so simple, but is so difficult to 

 understand as this. Tricyclists who have been in the 

 habit of managing any machine at once, are surprised to 

 find in this something which is utterly beyond them. 

 They cannot sit upon it for an instant, for so soon as they 

 are let alune it politely turns them off. When at length, 

 after much coaxing, they can induce it to let them remain 

 upon it, they find it goes the way they do not want. 

 Riding the Otto, like any other accomplishment, must be 

 learnt. Some seem at home on it in half an hour, others 

 take a week or more. It is not surprising that that quick 

 perception, in which ladies have so much the advantage 

 of men, enables them to quickly overcome the apparently 

 insurmountable difliculties which this machine presents 

 to the beginner. 



The rider when seated is above the a.xle of two large 

 equal wheels ; being then apparently in unstable equili- 

 brium, he would of necessity fall forwards or backwards if 

 some movement of recovery were not possible. The 

 t tto rider maintains his balance in the same way as the 

 pedestrian. If he is too far forward, pressure on the front 

 foot will push him back ; if too backward in po-ition, 

 pressure on the rear foot will urge him forward. That 

 this must be so is clear, for, whatever turning power he 

 applies to the wheels, action and reaction being equal and 

 opposite, they will produce an equal turning effect upon 

 him. The steering of this machine is quite [.eculiar. In 

 the ordinary way both wheels are driven by steel bands 

 at the same speed ; so long as this is the case, the Otto 

 of necessity runs straight ahead. When the rider desires 

 to turn, he loosens one of the bands, which causes the 

 corresponding wheel to be free ; if then he touches it 

 with the brake or drives the other wheel on, it will lag 

 behind, and the machine will turn. It is even possible to 

 make one wheel go forwards and one backwards at the 

 same time, when the machine will spin like a top within 

 a circle a yard in diameter. 



There being no third wheel the whole weight is 

 on the drivers, the whole weight is on the steerers ; 

 the frame, which is free to swing, compels the 

 rider to take that position which is most advantageous, 

 making him upright when climbing a hill, and com- 

 fortably seated when on the level. Owing to a curious 

 oscillation of the frame which occurs in hill climbing, the 



dead points are eliminated, so the rider need not waste 

 his strength at a position where labour is of no avail. 



Though it has been impossible for me to do more than 

 indicate in the most imperfect manner how numerous and 

 beautiful are the principles and devices employed in the 

 construction of C)cles, I trust I have disappointed those 

 who were shocked and horrified that so trivial a subject 

 should be treated seriously in this Institution. 



DANGERS FROM FLIES 

 T N a note communicated to the Gazzetta degli Ospilaii 

 ■*■ for August 1883, and republished in the current 

 number of the Archives Italicnncs de Biologic (tome iv. 

 fasc. ii.). Dr. B. Grassi calls attention to the fact that 

 flies are winged agents in the diffusion of infectious 

 maladies, epidemics, and even parasitic diseases. During 

 the summer season, when flies occur in swarms, it seems 

 impossible to prevent them from settling on any and 

 every object. In these countries, though sometimes 

 troublesome, they are scarcely ever so numerous as in the 

 warmer climates of the Continent, and even in these 

 latter they are not often to be found such plagues as they 

 are in Egypt ; but in all these countries alike they may 

 be seen to alight on all moist substances without distinc- 

 tion. It may be the expectorations of a phthisical or the 

 ejecta of a ty[.hoid patient that have last attracted these 

 inquiring diptera ; but, irrespective of the material they 

 may have been investigating, their next visit may be to 

 the moist lips or eyes of a human being. Their feet, their 

 mouth, and the pectoral portion of their bodies will have 

 all come in contact with the infective mass, and will all 

 in turn be more or less cleansed of it by the moisture of 

 the freshly visited mucous membranes. But this danger 

 has already been known and recognised, and it seems 

 scarcely doubtful that in Egypt ophthalmia is constantly 

 carried to the eyes of the infant natives by such winged 

 visitors. Dr. Grassi calls our attention to even greater 

 danger, and this from the ejecta of the flies themselves. 

 Every housekeeper knows how the bright surface of a 

 mirror or the gilt moulding of a picture-fraine can be 

 covered over with the little flecks left by these flies, — 

 no English words occur to us to translate therewith 

 the phrase " les mefaits des mouches." The following 

 experiences of Dr. Grassi relate to these: — At Rovellasca, 

 between his laboratory, which is on a first floor, and his 

 kitchen, w-hich is on the ground floor, there lies a court- 

 yard, with a distance between the windows of the two 

 rooms of about ten metres. On a plate on the table of 

 his laboratory he placed a large number of the eggs of a 

 human parasite (Trichocephalus). After a few hours he 

 found, on some white sheets of paper hanging in the 

 kitchen, the well-known spots produced by the excreta of 

 the flies, and on a microscopical examination of these 

 spots, several eggs of the parasite were found in 

 them. Some flies coining into the kitchen were now 

 caught, and their intestinal tract was found quite filled 

 with an enormous mass of foecal matter, in which the 

 presence of eggs of Trichocephali were detected. As it 

 was practically impossible to keep all alimentary sub- 

 stances from contact with these flics, it follows that the 

 chances of Dr. Grassi and his family being infected with 

 Trichocephali were very great. As a matter of fact, the 

 experiment was tried with non-segmented eggs of this 

 worm. Another experiment was in the same direction. 

 Dr. Grassi took the ripe segirents of a lania solium 

 (which had been in spirits of wine) and broke them up in 

 water, so that a great number of the tapeworm's eggs 

 remained suspended in the fluid. The flies came to the 

 mixture, attracted by the sugar, and in about half an hcur 

 the ova of the tapeworms were to be found in their intes- 

 tines and in the spots. Had these eggs been in a recent 

 and living state, they would doubtless have been just as 

 easily transported. To those who care to try these 



