A. As the cor'nea _is too flat_, the image of any near object is formed _behind the RET'INA of the eye_, and is not seen at all. [Illustration: The reflection is made at DE, instead of at ABC (the retina).] Q. _What sort of GLASSES do OLD people WEAR?_ A. As their cor'nea is _not sufficiently convex_, they must use _double convex glasses_, to enable them to see objects near at hand. Q. _What sort of glasses are DOUBLE CONVEX SPECTACLE-GLASSES?_ A. Glasses which _curve outwards_ on both sides. [Illustration: The figure A is double convex, or convex on both sides.] Q. _What is the USE of DOUBLE CONVEX spectacle-glasses?_ A. As the image of near objects is reflected _behind the RET'INA_, these double convex glasses _shorten the focus of the eye_, and bring the image _into the eye_ (upon the ret'ina). Q. _Why do NEAR-SIGHTED persons bring objects CLOSE to the eye, in order to SEE THEM?_ A. As the distance between the _front and back of their eye is too great_, distant objects are reflected _before they reach the ret'ina_; therefore, near-sighted persons bring the objects _closer_, in order that the reflection _may be cast further back_, (to reach the ret'ina). Q. _Why do OLD people HOLD objects FURTHER OFF, in order to see them better?_ A. As the distance between the _front and back of their eye is not great enough_, the reflection of near objects is thrown _beyond the ret'ina_; therefore, they hold objects _a long way off_, in order to bring their images _forward_ (so as to cast it on the ret'ina). Q. _Why are HAWKS able to see such an IMMENSE way off?_ A. Because they have a muscle in the eye which enables them to _flatten their cor'nea_, by drawing back the crystalline lens. This muscle is called the "marsupium." Q. _Why can HAWKS not only see such a long way off, but also objects within half-an-inch of their eye?_ A. Because their eyes are furnished with a broad circular rim which _confines the action of this muscle_, and throws the _cor'nea forward_. Q. _Into how many PARTS may a RAY of LIGHT be DIVIDED?_ A. Into three parts: BLUE, YELLOW, and RED. N.B. These 3 colours, by combination, make seven. 1.--RED. 2.--Red and yellow form ORANGE. 3.--YELLOW. 4.--Yellow and blue make GREEN. 5.--BLUE. 6 and 7.--Shades of blue called INDIGO and VIOLET. Q. _How is it KNOWN, that a ray of light consists of several different colours?_ A. Because, if a ray of light be cast upon a triangular piece of glass (called a prism), it will be distinctly divided into seven colours: 1.--Red; 2.--Orange; 3.--Yellow; 4.--Green; 5.--Blue; 6.--Indigo; and 7.--Violet. Q. _Why does a PRISM DIVIDE a ray of light into VARIOUS COLOURS?_ A. Because all these colours have _different refractive powers_. Red is refracted _least_, and blue the _most_; therefore, the _blue_ colour of the ray will be bent to the _top_ of the prism, and the _red_ will remain at the _bottom_.