II 



supply a larger lens, used on many modern cycle lamps, for sums from id. 

 upwards. These cheap lenses answer the purpose perfectly well. 



As for the " tinters," these are made of strips of cardboard which fit the 

 grooves ; each piece has a hole in the centre about an inch in diameter, and 

 over this is gummed a piece of tinted gelatine, such as may be found on Christ- 

 mas crackers red, blue, green, and so forth. 



Now let us examine the portion of the telescope used. Notice, first, that 

 the two top tubes are used, and not simply the top tube alone. Unscrew the 

 telescope at C, and make the hole in the top of the wooden stand just large 

 enough to take the screw-piece. There should be no difficulty in identifying 

 this, as it is marked clearly C in the diagram. 



The lowest power is obtained by shutting up the top tube DE into the 

 lower one CD. This is just making use of the " eyepiece " of the telescope 

 as it stands. 



The second magnification is obtained in the following way : You will 

 remember that when we took the telescope to pieces we found at D a little 

 tube with a powerful lens at each end, and a small diaphragm between. 



Here (Fig. 2) is a diagram of that objective. To increase your magnification 

 you must take out this compound lens, unscrew the top lens, marked C in the 

 diagram, and put the rest back in its place. You will now find on focusing 

 your object afresh that it appears at least twice as big as before. 



The third magnification is actually shown in the drawing of the microscope. 

 This time you put back your little lens C, and having thus reconstructed your 

 compound lens, you place it, not in its usual position at the end of the first 

 tube, but at the end of the second tube, and you open out the two tubes to 

 their farthest length (which is about 9 inches). Notice in the drawing the 

 end of the " objective " just protruding from the bottom tube. It is held there 

 in position by a small tube of cardboard, the edge of which can also be seen. 

 Now examine your object again, and you will have it appearing at least as 

 large again. (I have no means of accurately determining these magnifications, 

 but these are approximate.) 



The fourth magnification is obtained by taking off lens C again, and replacing 

 the rest of the objective in the same place at the bottom of the second tube. 



This is the greatest magnification obtainable by manipulating the telescope 

 lenses themselves, and will probably suffice most of my readers. But if the 

 extra lens (extracted from the sixpenny finder mentioned above) is dropped 

 into place (as suggested on page 10), you can now get two further magnifica- 

 tions : the first with the whole objective plus your extra lens inside it, the 

 second with the lens at C removed. 



You have now no less than six different " powers " or magnifications, and 

 to show the difference between first and last I have experimented with a 

 micro-slide of Volvox globator. With the first magnification I could see prac- 

 tically the whole cell full of these minute organisms. With the highest power 

 I could just get three of them into view in the field of vision. 



