334 



NATURE 



[February 3, 1898 



did, on the 1892 entries only, was very perplexing. However, 

 by persevering with the other years, it became increasingly plain 

 that the pinnacle was a false maximum ; in 1896 it was certain 

 that the true maximum lay well within the portion of the curve 

 included in the diagram. The explanation of the pinnacle then 

 became obvious ^ ; it was that the tolerance granted to those 

 horses who failed by only a little to qualify themselves, was ex- 

 tended considerably beyond the quarter second for which I was 

 prepared. The cases of 2' 30 "o" were few ; they do not appear 

 in the diagram, but their addition would be quite insufficient to 

 remove the difficulty, If the pinnacle were distributed among 

 two adjacent columns outside and to the left of the diagram it 

 would smooth away the incongruity, so I suspect that cases of 

 "under 2' 32" and down to 2' 30"" are habitually rated at a 

 trifle less than 2' 30". Consequently I had nD hesitation in 

 wholly disregarding the entries that helped to make the pinnacle, 

 namely, the whole of those contained in the first column to the 

 left in every one of the diagrams. The course thereupon became 

 clear and straightforward. I estimated the position of the mean 

 value for each year, from inspection of the curve of that year, 

 allowing myself to be somewhat biassed in estimating its point of 

 culmination by the curves of the adjacent years ; similarly as to 

 the probable error. Now that the curves are drawn, I see that 

 somewhat better fits might have been made, but they are close 

 enough to show the existence of a fair amount of correspondence 

 between the observed values and those calculated according to 

 the law of normal frequency. It is near enough to remove hesi- 

 tation in working with the arithmetic mean. 



I now come to the fundamental purpose of this memoir, which 

 is to point out the existence in the registers of the American 

 Trotting Association, of a store of material most valuable to 

 inquirers into the laws of heredity, which accumulates and 

 increases in value year by year. But it seems to me hardly 

 worth while to discuss hereditary influence on speed in horses, 

 unless the records of at least their sires and of their dams, and 

 those of each of their four grandparents, as well as their own 

 record, are all known. Even in this case (according, at least, 

 to my own theory) one quarter of the hereditary influences are 

 unknown and have to be inferred. It is practically impossible 

 to make an adequate collection of the names of horses who fulfil 

 the above conditions out of the entries in the" Trotting Register," 

 each search requiring many cross references and occupying a 

 long time, while the number of futile searches before attaining a 

 success is great. On the other hand, the breeders and pos- 

 sessors of these notably bred horses must be familiar with the 

 required facts, and would assuredly be delighted to have them 

 known. There need, therefore, be little difficulty in obtaining 

 materials for the much desired table. In the meantime I am 

 sending circulars to the chief breeders in America, in hopes 

 of making a start. 



The great need for genealogical data of an exact numerical 

 kind, by those who prosecute inquiries into the laws of heredity, 

 is the justification that I off"er fur submitting these remarks to 

 the Royal Society. 



Physical Society, January 21. — Mr. Shelford Bidwell, 

 President, in the chair. — Prof. Fitzgerald exhibited some photo- 

 graphs by Mr. Preston in illustration of the Zeenian effect, for 

 various cases, including those of iron, cadmium, zinc, and 

 sodium. These photographs and the method of obtaining them 

 have already been described. The cause of doubling is now 

 attributed by Prof. Fitzgerald to absorption by the surrounding 

 vapour. In a particular case he examined a double line that 

 exists in one of the photographs. Under the polariser the two 

 lines are at first distinctly seen ; but when the polariser is turned, 

 a thin line appears in the middle, and this central line is, there- 

 fore, circularly polarised in a direction opposite to that of the 

 outer pair of lines. The reason for the appearance of doubling 

 in the first position of the polariser is that the central line is 

 there completely absorbed out by the surrounding vapour. — 

 Prof. Oliver Lodge then gave a communication concerning his 



1 I should like to take the opportunity afforded by the appearance of an 

 abstract of my memoir in Nature to correct a questionable suspicion, 

 namely, that the pinnacles in the diagrams are due to tolerance shown 

 towards horses who failed by a very little to qualify for the much-coveted 

 rank of standard trotters. I am assured on excellent authority that the 

 strict conditions of timing make this impossible (among other reasons there 

 are three timers). On the other hand, there is a vast competition ///j^ to 

 pass the 2' 30" limit ; and when a horse has done so, his owner often does 

 not care to train him for racing, but rather to utilise him at once for breed- 

 ing or other purposes. The question is too complicated to discuss here at 

 length. Suffice it that the 2' 29" to 2' 30" records are not homogeneous 

 with the rest, and should be discarded as I proposed. — F. G. 



NO. 1475, VOL. 57] 



work on " Electric Signalling without Connecting- wires." From 

 the nature of the oscillatory disturbances emanating from any of 

 the customary forms of Hertz vibrator, syntony has hitherto been 

 only very partially available as a means for discriminating between 

 receivers. There is in fact so rapid a decrease in the amplitude 

 of the vibrations that almost any receiver can respond to some 

 extent. Discrimination by syntony is possible with magnetic 

 systems of space telegraphy where the magnetic energy much 

 exceeds the electric, i.e. as between two separated inductive 

 coils ; and by the use of such coils, appropriately applied, the 

 author has been able to attain fair syntony even with true Hertz 

 waves, i.e. he has constructed spark-gap oscillators, with 

 sufficient persistence of vibration, and syntonised resonators. 

 The "coherer" principle can be applied to either a purely 

 magnetic or to the Hertzian system. It was first used by Prof. 

 Lodge in devising lightning-guards, and afterwards in his 

 magnetic system of telegraphy by inductive circuits, each in 

 series with a Leyden-jar ; a pair of knobs in near contact, or 

 other over-flow gap, being provided in the receiving apparatus. 

 This was the first meaning of a " coherer " in the electrical sense 

 as used by Prof. Lodge. It referred to a single contact between 

 two metal knobs. The term has since been extended by others 

 to the filings-tube of M. Branly, and some confusion has arisen, 

 for M. Branly does not consider that simple coherence and break 

 explains fully the behaviour of his instrument. Prof. Lodge is 

 disposed to agree, for he finds that the resistance of almost any 

 form of coherer varies in rough proportion to the received im- 

 pulses, and that there are other peculiarities (to be mentioned 

 later). He is, therefore, inclined to think that the action cannot 

 after all be entirely explained as due to mere " welding," but 

 that there is something more to be learnt about it. The sensi- 

 tiveness of a coherer depends upon the number of loose con- 

 tacts ; it is a maximum for a single contact, i.e. for a needle- 

 point lightly touching a steel spring. With this sensitive 

 coherer, hardly any " tapping-back " is required for decoherence, 

 but it wants delicate treatment when properly adjusted, and the 

 greatest current through it should not approach a milliampere. 

 On the other hand, a Branly tube rather improves under rough 

 treatment ; in such a tube the author prefers to use iron filings 

 in the best possible vacuum ; brass, too, is very good, but rather 

 less easy to manage. Aluminium is thoroughly bad, and gold, 

 for an opposite reason, will not work — its surface is too clean. 

 Points, or small surfaces for making contact with the filings, are 

 better than large surfaces. The usual method of connecting the 

 coherer across the gap of an ordinary Hertz receiver, in parallel 

 with the telegraph instrument and battery, has the unavoidable 

 objection that they shunt away part of the received oscillations. 

 With the syntonic receiver of Prof. Lodge, which contains no gap, 

 but a closed wire coil instead, this difficulty no longer exists ; for 

 the coherer can now be in series with the detecting instrument, 

 and in so far as these obstruct the oscillations they may be 

 shunted out in various ways, as the author describes. The main 

 feature of his new syntonised vibrators is this self-inductance coil, 

 whose function it is' to prolong the duration of the oscillations, 

 and thereby to render syntony possible. Although such a coil 

 acts disadvantageously in so far as it possesses resistance, the 

 resistance does not increase so fast as the self-induction. 

 The coil should consist of thick copper of highest conductivity, 

 and it should have maximum inductance for given resistance. 

 For similar reasons, the capacity-areas should also be of highest 

 conductivity, their dimensions should increase outwards from the 

 spark-gap, as triangles. The receiver must have 110 gap, it 

 should be accurately bridged over when a transmitter is used as 

 receiver. The limit of speed of response depends upon the tele- 

 graphic instrument. Dr. Muirhead adapted a siphon-recorder 

 to the purpose, because it is one of the quickest responders ; he 

 arranged it so that it could be used with intermittent currents 

 direct. Under these intermittent impulses the siphon trembles ; 

 and instead of the ordinary siphon signals, the slip is marked 

 with dots and dashes. Constant mechanical tremor is usually 

 employed for decoherence, but the author finds that decoherence 

 can be brought about by electrical means, without any rnechanical 

 tremor, by connecting the coherer momentarily to a circuit less 

 effective as a collector than that of the proper capacity-areas of 

 the syntonised receiver. The battery and galvanometer detector- 

 circuit may be used for this purpose, the coherer being momen- 

 tarily connected to it, and while so connected letting it ex- 

 perience an impulse from a distance. Prof. Lodge has designed 

 a revolving commutator by means of which the coherer can be 

 rapidly changed over from the resonating circuit to the instru- 



