August 25, 1892] 



NATURE 



393 



of animals, but it differs in exactly the same way from my know- 

 ledge of that of all other men. If in no case is "an animal 

 activity to be interpreted as the outcome of the exercise of a 

 higher psychical faculty, if it can be fairly interpreted as the out- 

 come of one which stands lower on the psychological scale," 

 the same rule should be applied to the interpretation of human 

 activities, for the only reason for distinguishing between human 

 and animal psychology is that their activities do, as a matter of 

 fact, differ. Human beings are of course distinguished from 

 animals in other ways ; in the structure of their limbs, for 

 example ; but there is no a priori ground for inferring from such 

 differences any, and certainly not any particular, difference in 

 psychological powers. And so far from its being permissible to 

 infer such a difference from greater or less complexity of brain- 

 structure, it is only because animals which when alive displayed 

 great activities proved, on dissection, to have possessed complex 

 brain structure, that we can infer any connection whatever be- 

 tween the two phenomena. As no man has ever dissected his 

 own brain he cannot say that any particular structure is associ- 

 ated with those psychological powers of which alone he has any 

 more direct knowledge. If, for example, I say " Morality in- 

 volves a perception of the relation between the actual and ideal, 

 and is based on introspection," I say this in consequence of my 

 personal experience. I can only infer morality, introspection, 

 and so on, in other beings, whether animals or men, by judging 

 from their activities. And if " most cases of so-called morality 

 in the dog can be otherwise interpreted," so also can most cases 

 in other men. A fundamental distinction between the psycho- 

 logical powers of animals and men could only be established by 

 showing a fundamental distinction between animal and human 

 activities, as observed from outside by a third person. And 

 though it is easy to show that there is a difference in degree. 

 Prof. Morgan did not adduce any cases which even tended to 

 show that there is any difference in kind. The cases he did 

 adduce all tended the other way ; and though this was doubt- 

 less because he only adduced difficult cases in order to show that 

 his theory was capable of explaining them away, his explana- 

 tions seemed to me, for the reasons I have given, insufficient. 



Note. — The quotations are from a printed /r^cij of his paper 

 distributed by Prof. Lloyd Morgan at the meeting. 



Edward T. Dixon. 



12, Barkston Mansions, South Kensington, August 5. 



Tropical Cyclones. 

 A FEW years ago I drew up some simple mathematical rules 

 ;o aid the Jamaica Weather Service when in doubt as to the 

 indications, and thinking that these rules may be of some use to 

 other isolated or nearly isolated stations in the Tropics, I state 

 them here, and give an example or two as to their application. 

 At the time and place of observation let 



/ = Reading of bar in inches and decimals of an inch, 

 corrected for instrumental error, reduced to 32° F. 

 and sea-level, and further corrected for diurnal 

 variation. 

 pm = Mean value oi p for the time of the year. 

 Ap = pm - p = fall of pressure below the mean. 

 V — Velocity of the wind in miles per hour, 

 r = Distance of the centre of the cyclone in miles. 

 -^ = Bar-gradient, or the fall of / per mile towards the 



centre at the place of observation. 

 ^ = Rate of fall, or the fall oi p per hour. 

 dr 



dt 



Rate of approach of the centre in miles per hour. 



Now let us suppose that the centre is moving towards the 

 place ; in this case we have 



Rate of fall 

 Gradient 



(1) 



In Jamaica -t is found by an exchange of telegrams between 



Kingston and Kempshot, these places being on the line of usual 

 approach, and 77 miles apart 



NO 



191, VOL. 46] 



The next equation is based upon the results of observation 

 _ _A£ _ Fall below mean 



dr 



Twice the gradient 



(2) 



This equation must not be pressed ; it is intended to be used 

 when the centre is still a long way off. 

 Thus we have 



Time of arrival of the centre = -^ = 



Jt 

 Fall below mean 



Twice the rale of fall 



(3) 



This is an important equation, for it shows that the 'direct 

 approach of a cyclone may be ascertained ,;by the constancy in 

 the computed time of arrival. 



As an example, let us take the cyclone which passed over 

 Kingston, Jamaica, August 18, 1880. This was before the 

 Weather Service was established, and the indications of the 

 advancing cyclone were confused by the existence of a small 

 cyclone to the north-east of Kingston ; there was no wind in 

 Kingston until 8 p.m., and rain fell quietly in showers all that 

 afternoon from a sky covered with stratus. 



Kingston, Jamaica, August 18, 1880. 



From the last column it appears that from 7 a.m. to i p.m. 

 the cyclone was not directly approaching, and from the logs of 

 vessels and other information it is certain that the cyclone was 

 passing south of Jamaica on a westerly course, and that between 

 I and 3 p.m. it turned on its course and advanced directly to- 

 wards Kingston. The centre arrived at about 9 15 p.m., lowest 

 p = 28-917.^ A warning notice was posted at 3 p.m., but had 

 these rules been in existence, a better notice could have been 

 posted at 5 p.m. 



Now if the gradient be not known at an isolated station, it 

 may sometimes be deduced from the theoretical equation — 



dp 



dr 



o 000070 



.(4) 



This equation is only to be used for considerable distances from 

 the centre ; and if v be small, or variable, or if it be mixed up 

 with the sea-breeze, it cannot be used at all. 



If -^ be known, r is known from (2), and then some idea 

 dr 

 may be formed as to the magnitude of the coming disturbance. 

 The following rule may prove useful :— 



Let Ap^ be the fall below the mean at the calm centre of the 

 cyclone ; then, roughly — 



... = ^^^^(. 



3A/>V^ 



(5) 



dp 



Now ^ is unknown in the example above ; but if we take 

 dr 



— = 18 from the subsequently known circumstances, (i) gives 

 dt 



^ = 0-00I2 at 3 p.m. ; (2) gives r = lo6 at the same hour 



which happens to be right ; and (5) gives Ap^ = 1-3, which is a 

 little too large, the observed fall at the centre being about I'l. 



As another example, let us take the great hurricane in 

 Mauritius on April 29 this year. Some valuable notes by 

 Dr. Meldrum are published in Nature, June 9, but unfortu- 



» See " Jam.iica Mtteor. Obs," vol. i. (Introduction). 



