202 THE MENDEL JOURNAL 



extent upon the scrap-heap ; more efficient implements are 

 taking its place. Yet assuredly, in the days when it was 

 solely used, it was an incalculably valuable tool. So it 

 is with the working hypotheses of men of science ; like the 

 scythes and the sailing ships, they are the efficient in- 

 struments for the work of the day. But men of science 

 know that to-morrow and at successive periods they will be 

 supplanted by a better instrument, until one is found which does 

 its work ideally. And when in Science such a working hypo- 

 thesis has been found — one which does its work ideally — it is 

 called a " Theory," or if very ideal a " Natural Law." 



These " Natural Laws " wall probably never be surpassed or 

 replaced. They differ from hypotheses in their permanence. 

 In Science there are very few of them. The conditions of their 

 existence are rigid, severe, implacable, and onerous. They are 

 tested by facts unlimited and time illimitable. We may count 

 the number of them upon the fingers of our hands. It will not 

 be amiss, by way of illustration, to mention some of them. In 

 the Physical World there is the " Law of Gravitation," the " Law 

 of the Conservation of Energy and Matter," and in the Realm of 

 Biology there is the " Law of Evolution," and the " Law of the 

 Survival of the Fittest." 



Now what is it that a man of science understands by the term 

 " Law " ? He does not understand by it the same thing that a 

 legislator does. It is not a written code asserting what shall or 

 shall not be, or stipulating what we may do or may not do. To 

 him it is merely a statement of the consequences or results which 

 arise as the outcome of natural processes at work. It is 

 a generalised expression which accurately describes all the 

 detailed and particular phenomena to which the " Law " applies. 

 In other words, it is only a general way of describing the relation- 

 ship of a large number of particular events or facts, which are more 

 or less remotely related to each other. The "Law of Gravitation," 

 for instance, enables us to describe in uniform terms the falling of an 

 apple and of a feather ; but it also explains the rising of a balloon, 

 the floating of a ship, the swinging of a pendulum, the parabolic 

 path of a bullet, the motion of meteors, and the orbits travelled 

 by the moon, earth, and sun. The "Law of the Conservation of 

 Energy " similarly enables us to describe in consistent and uniform 

 language the production of electricity by the burning of coal ; 

 the formation of coal forests from the energy of the sun that 

 shone millions of years ago ; the production of heat and motion 

 in the human body by the. consumption of oxygen and other 

 elements ; the conversion of a sugary solution into an alcoholic 

 one by the activities of the yeast plant ; the growth of a man or 

 a bean plant from a microscopic egg under the influence of the 



