352 



NATURE 



[February 13, 1896 



.They are arranged in the order of the mean distances from the 

 sun. 



The mean distances of the comets from the sun range from 

 2 -2 1 8 to 3-854, but the aphelion distances do not vary so greatly 

 in proportion — a fact which suggests the controlling influence 

 of Jupiter. It is remarkable that such a small number of 

 regularly returning comets seem to be permanently attached to 

 our system. 



Effect of Spots on Sun's Diameter. — Observations of 

 the sun's diameter, made in the latter half of last year by J. 

 Sykora, of the Charkow Observatory, have led to a result which 

 may be of considerable importance if established by further in- 

 vestigations {Ast. Nach., No. 3330). The observations were 

 made with a 6-inch refractor by projecting the image of the sun 

 together with that of the micrometer wires. The diameter 

 measured in the direction of the points of appearance or dis- 

 appearance of spot groups was found in the great majority of 

 cases to be greater than the diameters in neighbouring parts of 

 the sun as measured on the same days. Some of the results are 

 as follows, the first column giving the diameter in the direction 

 of spot groups, and the other two showing adjacent diameters : 



It is concluded that although the spots themselves may be de- 

 pressions, they produce an elevation of the surface of the sun in 

 the regions where they are formed. 



THE SPECULATIVE METHOD IN 

 ENTOMOLOGY. 

 T^HE annual general meeting of the Entomological Society 

 of London was held on January 15, the President, Prof. 

 R. Meldola, F.R.S., being in the chair. After referring to the 

 affairs of the Society and to the great literary activity of English 

 entomologists during the past year, the President called atten- 

 tion to Mr. Oswald Latter's discovery of the secretion of 

 potassium hydroxide by Dicrantira vimila, &c. , and to Mr. F. 

 Gowland Hopkins's researches on the pigments of Pierine 

 butterflies. The address then proceeded as follows : — 



The association of chemistry and biology in researches such 

 as those to which I have drawn attention, has suggested a com- 

 parison between the methods of research in vogue in the two great 

 departments of science of which thef^e two subjects are respec- 

 tively typical. All science necessarily begins with observation 

 or experiment, i.e. with ascertained facts, and it is perhaps 

 unnecessary to assert that no mere collection of facts can con- 

 stitute a science. We begin to be scientific when we compare 

 and coordinate our facts with a view to arriving at generalisa- 

 tions on which to base hypotheses or to make guesses at the 

 principles underlying the facts. Having formed the hypothesis 

 we then proceed to test its accuracy by seeing how far it enables 

 us to explain or to discover new facts, and if it fails to do this to 

 our satisfaction we conclude that our guess has been a bad one 

 and requires modification or replacing by a better one, i.e. by 

 one more in harmony with the facts. I take it that the course 

 of progress is the same in so far as these fundamental methods 

 are concerned in both departments of science, the physical and 

 the biological. It is possibly a matter of individual opinion as 

 to how large a body of facts should be accumulated before we 

 attempt to draw any general conclusions. There can be no 

 ■doubt that the requirements of one branch of science cannot be 



NO. 1372, VOL. 53] 



measured by those of another branch to which it has no near 

 relationship. But however large the number of facts, and 

 however cautious or conservative the worker may be, it is ar» 

 established doctrine taught by the whole history of science, that 

 real progress only begins when we go to seek for facts aimed 

 with at least the suggestion of a principle if not with a complete 

 theory based on facts already accumulated by observation or 

 experiment. This is the whole difference between scientific 

 observation or experiment and mere random or haphazard 

 observation. A naturalist of the old school, William Swainson, 

 writing in 1834,^ speaks of the " observance of nature, without 

 making any attempt to generalise the facts so acquired," as. 

 "a mere amusement, fascinating indeed, and even useful, but 

 totally disconnected with the objects of philosophic science." 

 Now I venture to think that entomology in this country has been 

 retarded in its development for want of a little more of thi.s 

 " philosophic science" ; by an unwillingness on the part of our 

 most active workers to give rein to the imagination — by an 

 overcautiousness which is damping to the speculative faculty. 

 There are no doubt many present who will not agree with this- 

 view, but I claim indulgence while I state my casein its support. 

 It will, I think, be conceded that we have passed beyond the 

 mere fact-collecting stage. It appears to me that in entomology 

 we have arrived at a state where we are suffering from a plethora 

 of facts ; if we are not in a position to explain everything con- 

 nected with the development, life-histories, instincts, classifica- 

 tion and distribution of insects as a class of animals, we are at 

 any rate in a position, speaking paradoxically, to know what we 

 want to know, and I do not see how we are going to advance 

 unless a more generous use is made of hypothesis as a scientific 

 guide. It is this point which I desire to urge and to show that 

 there is no real danger in boldly facing what the late Dr. 

 Romanes aptly calls the bugbear speculation. 



In .the first place, with respect to the physical sciences, there 

 is abundant justification for the view which I am advocating. We 

 have there long ceased to collect random facts ; observations 

 and experiments are suggested by hypothesis. That prince 

 among experimental philosophers, Michael Faraday, was wont 

 to say : " Let us encourage ourselves by a little more imagination 

 prior to experiment." The state of affairs is well summed up 

 in one of the latest works on chemistry in which the author, in 

 introducing the fundamental principles of modern investigation 

 says : 



" The history of the exact sciences teaches us that we may 

 discover new laws of nature in two essentially different ways, 

 one of which may be designated as the empirical, ■ the other 

 as the theoretical. Thus in one way by suitable observa- 

 tions, one collects abundant material . . . and then by a 

 repeated and purely empirical grouping of the data so obtained, 

 he seeks to approach the desired goal. . . . The second way, 

 on the other hand, leads from suggested conceptions regarding 

 the nature of certain phenomena, through pure speculation to 

 new information, the correctness of which must be determined 

 by a subsequent research." - One other recent utterance by my 

 colleague. Dr. W. M. Hicks, the President of Section A at the 

 last Ipswich meeting of the British Association, will serve to 

 give us a glimpse into the spirit of progress in pure physics : 

 " By our imagination, experience, intuition, we form theories; 

 we deduce the consequences of these theories on phenomena 

 which come within the range of our senses, and reject or modify 

 and try again. It is a slow and laborious process. The wreck- 

 age of rejected theories is appalling ; but a knowledge of what 

 actually goes on behind what we can see or feel is surely, if 

 slowly, being attained. It is the rejected theories which have 

 been the necessary steps towards formulating others nearer the 

 truth." » 



And now let us consider how far these methods, recognised 

 as valid in the physical sciences, are applicable to the biological 

 sciences, of which entomology constitutes a branch. Of course, 

 I am not claiming for our subject the position of an exact 

 science, and to suppose that it could be advanced by purely de- 

 ductive methods would be absurd. But I am endeavouring to 

 hold the balance Iietween a more liberal use of the speculative 

 method, on the one hand, and the deadening influence of refusing 

 to speculate at all, on the other hand. I am putting forward a 

 plea for an increased use of the imagination, because I hold that 



1 ' Preliminary Discourse on the Study of Natural Science," p. 51. 



2 " Theoretical Chemistry," by Walter Nernst, translation by Prof. 

 Palmer, 1895, p. 2. 



3 Address to the Mathematical and Physical Section of the British 

 Association, Ipswich 1895. 



