The sun paints a million images of the same object, and each observer has a perfect picture. It makes common to all mankind the beauties of nature, and paints as richly for the peasant as for the king. The Siamese twins were united by a living cord which joined their systems, and gave unity and sympathy to their sensations. In the great flood of light that daily bathes the world, we have a bond of union, giving the like pleasures and inspirations to millions of people at the same instant. And that which floods the world with beauty, should no less be a bond of unity and love. CHAPTER XXVII. 561. _What is electricity?_ Electricity is a property of _force_ which resides in all matter, and which constantly seeks to establish an _equilibrium_. 562. _Why is it called electricity?_ Because it first revealed itself to human observation through a substance called, in the Greek language, _electrum_. This substance is known to us as _amber_. 563. _In what way did electrum induce attention to this property of force in matter?_ Thales, a Greek philosopher, observed that, by briskly rubbing _electrum_, it acquired the property of _attracting_ light particles of matter, which moved towards the amber, and attached themselves to its surface, evidently under the influence of a _force_ excited in the amber. 564. _What is amber?_ It is a _resinous_ substance, hard, bitter, tasteless, and glossy. It has been variously supposed to be a vegetable gum, a fossil, and an animal product. It is probably formed by a _species of ant_ that inhabit pine forests. The bodies of ants are frequently found in its substance. [Verse: "He made darkness his secret place: his pavilion round about him were dark waters and thick clouds of the skies."] 565. _Why does the rubbing of a stick of sealing-wax cause it to attract small particles of matter?_ Because it excites in the sealing wax that _force_ which was first observed in the _amber_. Sealing-wax, therefore, is called an _electric_ (_amber-like_) body. 566. _Why do we hear of the electric fluid?_ Simply because the term _fluid_ is the most convenient that can be found to express our ideas when speaking of the _phenomena of electric force_. But of the nature of electricity, except through its observed _effects_, nothing is known. 567. _What substances are electric?_ All substances in nature, from the _metals_ to the _gases_. But they differ very widely in their electrical qualities. 568. _What is positive electricity?_ Electricity, when it exists, or is excited, in any body, to an amount which is _in excess_ of the amount natural to that body, is called _positive_ (called also _vitreous_). 569. _What is negative electricity?_ Electricity, when it exists, or is excited, in any body, in an amount which _is less_ than is the amount natural to that body, is called _negative_ (called also _resinous_).