igo SCIENTIFIC ILLUSTRATIONS [Law 



The "Ordinary Law" and the "Whole Law" 

 Distinguished. 



Many mistakes and many debates arise because men do not 

 distinguish the difference between that which is an ordinary 

 law and that which is the whole law. Let us illustrate this 

 by the following example : Every one knows that " fire burns," 

 and if we touch what is red-hot, it will most painfully blister 

 the skin, arid that if the contact be prolonged only for a few 

 seconds, the flesh will be destroyed with inexpressible torment. 

 This is the ordinary law of Nature, and what we naturally con- 

 ceive to be the whole of the law of Nature regarding the action 

 of fire and of red-hot substances. But if a quantity of lead be 

 melted, and made so hot that it seems incapable of any further 

 increase of temperature, the hand may be dipped into it without 

 sustaining the slightest injury, without being in the slightest 

 degree burned. This is well known to chemists ; and men with 

 nerve enough to make the plunge have many times proved it to 

 their startled friends and pupils. LI. 



The Pitfalls of the Law. 



The insect known as the ant-lion, in its larval condition, is 

 truly a wonderful being. A ruthless destroyer of insects, it 

 chooses some sandy spot where the soil is as far as possible free 

 from stones, and begins to form the celebrated pitfalls by which 

 it is enabled to entrap ants and other insects. Crawling back- 

 wards in a circular direction, it traces a shallow trench, the 

 circle varying from one to three inches in diameter. It then 

 makes another round, starting just within the first circle, and 

 so it proceeds, continually scooping up the sand with its head 

 and jerking it outside the limits of its trench. By continuing 

 this process, and always tracing smaller and smaller circles, the 

 grub at last completes a conical pit, and then buries itself in 

 the sand, holding the mandibles widely extended. Should an 

 insect, an ant, for example, happen to pass near the pitfall, it 

 will be sure to go and look into the cavity. No sooner has the 

 ant approached the margin of the pitfall than the treacherous 

 soil gives way, the poor insect goes tumbling and rolling down 



