NA TURE 



[November 2, 1899 



as it is, can be made to rise, fall or rotate by an almost 

 imperceptible movement of the hands, possibly after a 

 time unintentionally on the part of the water-diviner, 

 and the public is impressed. For the same reason it may 

 be well to find that water can only be met with in some 

 inconvenient position, such as under a haystack or the 

 cellar of the house, or the corner arch of a large granary. 

 Ignorant and credulous people will have much more faith 

 in you if you put them to a little mconvenience. 



If the water-finders would leave it here, there could be 

 no cause of complaint, provided, of course, that they 

 succeed where geologically trained people fail. But when 

 they put forward preposterous " scientific explanations " 

 such as I have extracted, it makes it very difficult not to 

 come to the almost inevitable conclusion that the water- 

 finder has no case, and that the surcharging of his fees 

 by auditors is necessary for the protection of public 

 bodies. Perhaps among the 130 references in the Bible 

 to the rod, staff or sceptre already referred to is this, " a 

 whip for the horse, a bridle for the ass, and a rod for the 

 fool's back." C. V. Boys. 



HISTOR Y OF THE ART OF EXPERIMENTING. 

 Geschichte der Physikalischen Experimentierkunst. Von 



Dr. E. Gerland und Dr. F. Traumuller. Pp. 427. 



(Leipzig : Wilhelm Engelmann, 1899.) 



THIS work, illustrated by more than four hundred 

 woodcuts, gives a most interesting account of the 

 apparatus used and of the investigations made by scien- 

 tific inventors from the earliest times at which records 

 exist down to the invention of Morse's printing telegraph 

 in 1843. 



One of the most interesting things that appears on the 

 face of this history is the great mechanical ingenuity of 

 many of the inventors of ancient times, as, for example. 

 Hero of Alexandra, who invented a penny-in-the-slot 

 machine, and the almost entire absence of any attempt to 

 carry out what we would now call an experimental in- 

 vestigation. The experimental investigation of natural 

 phenomena is extraordinarily modern, and the looking 

 for mere rules of sequence in the phenomena rather than 

 transcendental souls, spirits, effluvia, and such like effi- 

 cient causes, is still more modern. This history covers 

 a period of some four thousand years ; but experimental 

 science of the modern type is not more than three hun. 

 dred years old. It is only amongst scientific men that 

 the nature of experimental inquiry has been appreciated 

 for as long as three hundred years. The well-educated 

 man has not ^appreciated its nature for more than fifty 

 years, and it is only within the last few years that in 

 Britain the characteristic nature of experimental science 

 has been at all generally understood. Even now a person 

 is considered well educated who does not understand how 

 to learn from experiment and observation to regulate his 

 life. As a consequence, many so-called well-educated 

 persons make awful fools of themselves. 



In addition to the history of the subject, there are in 

 connection with each period interesting resumes of its 

 peculiarities, and of how it was an advance on its pre- 

 decessors and yet did not attain to the position of sub- 

 sequent workers. For example, attention is called to the 

 NO. 1566, VOL. 61] 



way in which Gilbert, though in many ways imbued with 

 the modern spirit of experimental inquiry, was still so 

 dominated by the notion that magnets were possessed 

 with some sort of soul or spirit that he cannot be rightly 

 classed amongst the moderns, but is a sort of connecting 

 link between them and mediaeval superstitions. 



There are two interesting questions that are not solved. 

 One concerns the connection between Archimedes' ob- 

 servation in his bath, the method he employed to discover 

 the amount of alloy in King Hero's crown, and the 

 principle he enunciates in his writings as to the loss of 

 weight of bodies immersed in a liquid. There seems no 

 doubt from the description of the experiments he made 

 (by observing the rise of water in a vessel when gold and 

 silver were immersed in it) that he did not use weighings 

 at all in his determination of the alloy in the crown. It 

 would be interesting to know how he then discovered the 

 amount of loss of weight of a body immersed in a liquid. 

 What set him on observing this ? The question is the 

 more interesting in that most of the scientific workers of 

 that age seem to have confined themselves to solving 

 practical difficulties in the way of carrying out some 

 project they had in hand, and were not at all imbued 

 with the modern spirit of experimental research. The 

 other question that needs elucidation is as to the observ- 

 ation of the Florentine Academicians that water could 

 penetrate gold. This experiment used to be very com- 

 monly quoted to prove the ultimate porosity of solids, but 

 it does not seem to ^have been repeated, and there are 

 very grave doubts as to the genuineness of this pene» 

 tration. It seems much more likely that the gold cracked, 

 and that the Florentines did not observe this. 



It has several times happened that all the necessary 

 principles mvolved in subsequent inventions have been 

 discovered, and attempts made to apply them long before 

 the inventions were brought into actual use. In most 

 cases it seems to have been the want of ineans or of 

 push of the inventor that prevented him from getting his 

 invention into use. There is a generally received notion 

 that this want of success has been usually due to want 

 of practical abihty to get over difficuUies that arise 

 in actual use. This seems to have been true to only 

 a very small degree. .\ very remarkable instance of 

 an old invention coming into use is that of heat 

 engines. Hero of Alexandria invented several forms 

 of heat engine, including that latest development of 

 steam engines a turbo-motor ; yet it was only during 

 last century that any serious use was made of them, 

 unless imposing on the worshippers in Egyptian temples 

 can be called a serious use. The rate of evolution 

 of the steam engine has been most remarkable. In- 

 vented by Hero, it languished in an amoeboid condition 

 for many centuries, and then within two hundred years it 

 developed into its present highly organised family of 

 many genera and species. If a future geologist were to 

 exhume the remains of steam engines, and were to have 

 some means of determining the ages that elapsed be- 

 tween Hero's engines and that of Savery, and from these 

 data were to evolve a chronology of the recent develop- 

 ments, he could hardly avoid concluding that it took at 

 least a million years to develop the engines of a modern 

 steamship from Savery's engine. Many other forms of 

 engine have been proposed. Huygens' gunpowder engine 



