462 



NA TURE 



[September 5, 1901 



of their nervous organisms to stimuli similar to those which 

 have for ages incited their forerunners. 



The hot of horses has been hatched from the egg inside the 

 stomach of its host. After some nine months' residence in the 

 intestines, it is passed with the freces and subsequently becomes 

 the bot-fly. Until it becomes a perfect insect it has never seen the 

 outside of a horse, and yet, as soon as it sees one, it knows 

 exactly where to deposit its eggs in a position from which they 

 can be licked off and swallowed in their turn. The sight and 

 perhaps the smell of the horse is sufficient to inspire the here- 

 ditary desire to deposit eggs in a particular spot. If the stimulus 

 and its reaction were insufficient, that particular bot-fly would 

 cease to propagate. .. 



The garden spider, again, hatched from an egg laid the pre- 

 vious autumn, brings an enormous amount of hereditary skill into 

 the vicissitudes ol its life. It selects its site, builds its web, adapts 

 it according to the most approved plans to fortuitous circum- 

 stances, and distinguishes between harmless flies and dangerous 

 wasps with an innate cunning which is an exact replica of the 

 actions of the last year's brood. The nest of the trapdoor spider, 

 too, is quite as wonderful a production as the nest of any bird. 



Caterpillars, when they have reached their full growth, display 

 great skill in selecting appropriate hiding places in which to 

 pass into the chrysalis form, and those which weave cocoons do 

 so in recognised stages. Huber has described one which makes, 

 by a succession of processes, a very complicated hammock for its 

 metamorphosis ; and he found that if he took a caterpillar 

 which had completed its hammock up to .say the sixth stage of 

 construction, and put it into a hammock completed only to the 

 third stage, the caterpillar did not seem puzzled, but completed 

 the fourth, fifth, and sixth stages of construction. If, however, 

 a caterpillar were taken out of a hammock made up, for instance, 

 to the third stage, and put into one finished up to the ninth 

 stage, so that much of its work was done for it, far from feeling 

 the benefit of this, it was much embarrassed, and forced even to 

 go over the already finished work, starting from the third stnge 

 which it had left off at, befoi'e it could complete its hammock. 

 In this experiment it would appear that each instinctive action 

 calls other actions in definite order, and unless the proper 

 sequence is maintained the intelligence of the insect is unequal 

 to bridging the gap. 



Now let us apply the facts and inferences aforesaid to the 

 nesting of the chaffinch. We have seen how habits acquired 

 during the life-time of the individual impress themselves upon 

 the nervous connections, until, when the accustomed stimulus is 

 applied, they become quite independent of the will. We have 

 seen how certain reflex phenomena which are necessary for the 

 life of the individual have, through congenital connections, be- 

 come so automatic, that they take place whether the brain is 

 present or not. We have seen how habits of wild animals have, 

 through similar nervous bonds, been handed down to tame 

 descendants long after the said habits were useless and even 

 detrimental. We have noted that ancestral habits may lie in 

 abeyance until some perhaps unexpected stimulus arouses them — 

 for instance, the scraping of chickens when placed upon gravel, or 

 the diving of a water-bird upon sudden fright. We have ascer- 

 tained that many of these instincts are certainly not due to 

 instruction by older animals, but are purely spontaneous ; that 

 in insects these spontaneous actions are often most complicated, 

 and are sometimes not only carried out in definite order, as in 

 the weaving of their cocoons, but cannot be carried out except 

 in that definite order. 



The inference I draw is that the nest-building of the chaffinch 

 is due to a succession of reflexes. You remember that when Alice 

 was wandering about in Wonderland, she was continually coming 

 upon medicine-bottles, marked " Drink me," or upon pieces of 

 cake, marked " Eat me." You remember that when Alice 

 obeyed these directions strange things happened. Alice was 

 able to decipher her labels by the result of long and painful study 

 in her nursery. Had they been written in the Cuneiform 

 character, though perhaps perfectly intelligible to another, they 

 would have conveyed nothing to her. The nervous system of 

 the chaffinch has been educated by generations of hereditary ex- 

 periences, and when the newly-wedded chaffinch pair start upon 

 their housekeeping, they see in their mind's eye, upon some suit- 

 able site, a label marked " Build here " ; they go through the 

 stages of their architecture much as the caterpillar spins the 

 different stages of its cocoon, each stage suggesting its successor ; 

 and each twig, hair, or feather which they use, bears upon it a 

 label, "Use me next." 



THE EDUCATION OF ENGINEERS. 



SEVERAL papers on the training of engineers have recently 

 come under our notice, and it seems worth while to bring 

 together some of the expressions of views upon this important 

 subject. It is difficult, if not impossible, to lay down any hard 

 and fast line as to the course to be adopted by a youth who 

 wishes to become a qualified engineer, for the way to follow 

 must depend largely upon the position, age, prepotency and 

 previous training of the aspirant. Assuming, however, that the 

 principles of science have been studied at school, with practice 

 in the physical laboratory, the question is, what is the next step 

 to be taken ? The answers to this are many and various, as will 

 be gathered from the following notes from recent papers on the 

 subject. 



A paper on the training of electrical engineers, read by Dr. 

 J. T. Nicolson before the Manchester section of the Institution 

 of Electrical Engineers and published in the Journal of the 

 Institution (May 1901, No. 150), with the discussion upon it, 

 contains some noteworthy statements. The province of the 

 laboratory in the scheme of electrical engineering is. Dr. Nicolson 

 remarks, first to extend scientific knowledge by providing more 

 experimental data ; secondly, to show the student the scope, 

 value and limitations of the theories he has studied in the class- 

 room ; and thirdly, to provide object-lessons on the general trend 

 of electrical engineering design by means of machines and in- 

 struments of the newest types procurable. 



Theory must not, however, be neglected. ' ' Resting on a strong 

 foundation of mathematics, physics and chemistry, the know- 

 ledge of the engineer must always include such pure sciences as 

 those of kinematics, dynamics, hydrodynamics, thermodynamics 

 and electrodynamics. A sound elementary acquaintance with 

 all of these is necessary, and a specialised knowledge of that one 

 more particularly useful to the engineer in his own branch must 

 be obtained. It is, for instance, quite hopeless to try to explain 

 to a man who has no knowledge of dynamics, upon what 

 principles one proceeds in endeavouring to balance a loco- 

 motive. No amount of laboratory experiment will enable him 

 to dispense with a knowledge of the mechanical principles in- 

 volved. Again, the fundamental principles of thermodynamics 

 may not be of much use in helping a man to fix the size of the 

 cylinders of a steam engine ; but they will, at all events, keep 

 him from wasting his time in trying to design a perpetual- 

 motion machine, and they will show him how far he can hope 

 to go in the direction of the improvement of his heat motors, or 

 other energy transfoimers." As Prof Perry has said: — "An 

 electrical engineer must have such a good mental grasp of the 

 general scientific principles underljing his work that he is able 

 to improve existing things and ways of using these things." 



This latter qualification, a knowledge of theory, he must 

 acquire by private study and from his college lectures ; the 

 former will be best inculcated by experimental work in the 

 laboratory. In the electrical profession, considerable difference 

 of opinion exists concerning the stage at which a youth should 

 enter the works, if he is free to choose. Dr. Nicolson hplds 

 strongly the opinion that, after leaving school, the boy who 

 intends to become an electrical engineer should first spend at 

 least two years in the workshops of a mechanical engineer. 

 Here he will learn the elements of smithing, moulding, paitern- 

 making, fitting, machine-work and erecting. In this time he 

 cannot help picking up the names and appearance of the com- 

 mon implements and processes fundamental to all kinds of 

 engineering practice. Having put in two years in a mechanical 

 engineering workshop, Dr. Nicolson thinks the student ought 

 to enter an engineering college at about the age of eighteen, and 

 he ought to study there for not less than three years. 



"This last portion of his laboratory time should be devoted by 

 our embryo electrical engineer to what is, in America, called 

 ' thesis ' work. This is of the nature of an experimental 

 research, carried out either by the student himself or by a small 

 group of students of which he is one. Very much valuable 

 information has been obtained in American colleges in this way, 

 regarding the various types of new apparatus continually coming 

 out ; and it is found that the students learn, in the c.mrse of 

 such work, to assume responsibility by being in a large measure 

 left to their resources. Such investigation usually requires 

 either special apparatus or the loan of new types of machineiy ; 

 but good work may also be got by making progressive tests of 

 an operating plant either in the college or elsewhere." 



In the discussion upon Dr. Nicolson's paper, the view that 



NO. 1662, VOL. 64] 



