470 



NATURE 



[February 17, 1910 



•diameter of the wheel centre over the pads of the springs 

 being slightly less than that of the channel rim, the wheel 

 •centre can be inserted therein, but is not connected in any 

 way with it. The wheel is then complete and ready to be 

 used on a vehicle. 



The action of these wheels is simple, and merely consists 

 of the pads on the ends of the spiral springs, as it were, 

 acting as feet, which walk round inside the outer rim, and 

 in turn support the weight of the vehicle. The wheel 

 centre, when the vehicle is travelling along, rotates slightly 

 more rapidly than the outer rim, the advance of the one 

 upon the other being termed the " creep." When any 

 obstacles are passed over, the shocks imparted to the rim 

 of the wheel, which would, if it were a solid one, be trans- 

 mitted through the axle to the machinery and car body, 

 are absorbed by the rubber pads and springs before they 

 reach the wheel centre. The principle and details of this 

 wheel are quite novel, as has been admitted by the German 

 Patent Office experts previous to granting the patent. 



Owing to the rubber caps at the extremities of the spiral 

 springs being capable of deflecting in all directions within 

 certain limits, the friction of the moving parts of the wheel 

 is negligible, and, as a result, practically no heating occurs. 



X 



800 

 700 



eoo 



500 



saving in maintenance of each car, as regards tyres, bv 

 the use of " Panflex " wheels. 



In conclusion, the author enumerated the advantages 

 possessed by the " Panflex " wheel, and explained that bv 

 its adoption the use of the motor-car could be brought 

 within the reach of persons who are now precluded from 

 availing themselves of it owing to the excessive cost of 

 maintenance of the tyres. 



•400 

 300 

 200 



consequently the wear and tear is exceedingly small. The 

 spiral springs attached to the wheel centre are designed so 

 •that in no case can they be subjected to a strain in any 

 direction whichever approaches their limit of elasticity ; 

 •consequently, provided no flaw exists in the steel of which 

 they are made, their life should be indefinitely long. If- 

 however, from any cause a spring should break, no in- 

 convenience is felt, as the journey can be completed, and 

 a fresh spring can then be fitted in about five minutes. 



The repairs of the " Panflex " wheel merely consist of 

 the renewal of the solid rubber tyre, which can be effected 

 by a coach-builder, and probably an occasional rubber pad 

 or spring, a few of which should be kept in the car. The 

 wheels have been tested on the Daimler car for 4000 miles, 

 and the results indicate that the perishable parts should 

 endure at least 10,000 miles. 



These wheels have also undergone very severe tests on a 

 taxi-cab in the streets of London and the suburbs for the 

 last three months with very satisfactory results. The first 

 cost of the " Panflex " wheel is somewhat greater than 

 that of a pneumatic-tyred wheel, but the expenditure on 

 maintenance is much less, as is shown by the diagram 

 exhibited by the author (Figs. 4 and 5), which indicates" the 

 MO. 2103, VOL. 82] 



THE SPECTRUM OF THE ZODIACAL LIGHT. 



CINCE the time when Cassini published his observations 

 •^ of the Zodiacal Light, in 16S2, the question as to the 

 nature and origin of this peculiar phenomenon has been 

 constantly recurring. Visual observers were ever at 

 variance on the subject, some holding the view that the 

 Light was a terrestrial adjunct, others that it was a solar 

 appendage. Visually, the matter is a difficult one to 

 decide, for no optical power may be used because of the 

 lack of contrast between the Light and its background of 

 sky. Photography is similarly placed out of court, but it 

 was expected that the question would be solved by the 



spectroscope. This 

 expectation has 



never yet been 

 realised absolutely, 

 but the results 

 recently published 

 (Lick Observatory 

 Bulletin, No. 165) 

 b\' Dr. Fath clarify 

 matters consider- 

 ably. 



Previous spectro- 

 scopic observations 

 have varied on a 

 vital point, viz. the 

 presence or absence 

 of bright radiations 

 in the spectrum, 

 indicating, by their 

 presence, that the 

 Light was self- 

 luminous. Thus 

 some observers 

 found that the spec- 

 trum was continu- 

 ous, others found 

 that its continuity 

 was broken by 

 bright bands, especi- 

 gQ — — gg — ally the bright 

 Thousands of Miles, aurora line at 

 5 ^ 5571- The argu- 

 ment for the pres- 

 FiG. 5. ence of the latter 



as an inherent 

 element of the spectrum was, however, considerably 

 weakened, if not eliminated, by the observations of 

 Respighi, Vogel, Piazzi-Smyth, and others, who were 

 unable to find the aurora line, when observing the 

 spectrum of the Zodiacal Light, unless it was at the 

 same time to be seen in all parts of the sky. Tacchini, 

 Cacciatore, and Ricca similarly were unable to find it, but 

 agreed that the spectrum was continuous, extending from 

 about X 5000 to \ 5550, with its maximum intensity at 

 ^ 535° ; that is to say, the spectrum of the Light re- 

 sembled the solar spectrum without the absorption lines. 



The detection of the dark solar lines is a difficulty 

 inherent to the observation, for the flight is so faint that, 

 to get a visible spectrum, a broad slit is essential, and 

 with a broad slit the comparatively fine absorption lines 

 are lost. 



Wright, in 1874, was able to use a narrower slit, and 

 found that the spectrum, with an intensity-curve simil.ar 

 to that of daylight, showed traces of an absorption band 

 in the position of the 5 band in the solar spectrum. 



Thus it became fairly evident that the Zodiacal Light 

 was reflected sunlight, and the opinion now generally held 

 is that it is reflected by a collection of small meteoritic 



Velars.. 



