116 QUESTIONS ON THE 



119. What is that science termed which explains the 

 doctrine of reflected light ? 



120. How are bodies seen ? 



121. What is meant by Vision ? 



122. Of what shape must the eye necessarily be? 



123. What is that membrane of the eye termed on 

 which objects seen become painted ? 



124. Which are the humours of the eye, and explain 

 them? 



125. By what contrivance is the idea of the images 

 of bodies seen conveyed to the brain ? 



126. If the object seen be delineated in an inverted 

 position on the retina of the eye, how is it that it ap- 

 pears to us in its natural position ? 



127. As the object seen is painted on the retina of 

 each eye, how is it that it does not appear double ? 



128. Of what particular shape are the eyes of such 

 persons as are near-sighted, and what kind of glass 

 must they use to rectify their vision ? 



129. How does age generally affect the shape of the 

 eye? 



130. Which are the seven primary colours ? 



131. How is the idea of colour produced in our 

 minds ? 



132. What is meant by the Spectrum ? 



133. How does Sir Richard Phillips explain colour? 



134. If the spectrum be divided into 360 parts, what 

 are the proportional parts of each colour ? 



135. The seven primary colours are reduceable to 

 three ; which are those three ? 



136. Which colour is most refrangible, and which 

 least refrangible ? 



137- What is understood by homogeneous, and what by 

 heterogeneous light ? 



138. Why does the sun appear of a red colour on a 

 hazy morning ? 



138. From what does the whiteness and from what 

 does the blackness of bodies arise ? 



139. What space of time would a ray of light take to 

 travel from the sun to each planet individually ; Mer- 



