THE SIMPLE MICROSCOPE. 



51 



to the object. To remedy this inconvenience, the author has 

 found the following contrivance extremely useful, a section 

 of the lens and cell in which it is contained being represented 

 by fig. 29. The semicircular spring is retained, its ends are 



seen in section at b b, and 

 entire in fig. 30 at d, land a 

 ring, a a, is adapted to it, 

 rather less in diameter than 

 the spring, and three-eighths 

 of an inch in depth ; it has a 

 shoulder or rim at one end. 



m 



•Fig. 29. 



and also two steel pins, c c, screwed in near the top edge, 

 exactly opposite each other ; these pins are received by two 

 holes made in the semicircular spring, so that the cell may 

 turn or swing upon the pins just as a compass on its gimbals. 

 The lenses are made to drop into this cell, and it will be 

 readily seen by fig. 30, which is a representation of the arm 



Fig. 30. 



and cell, just one-half its real size, that in whatever position 

 the arm is placed, the cell carrying the lens will be always hori- 

 zontal : — a exhibits the piece of brass forming the connection 

 between the two parts of the arm, it has a socket at one end, 

 in which the ball, b, works ; c is the small wire arm supporting 

 the spring, d; e is the cell which carries the lenses; 2 repre- 

 sents the situation of the cell when the arm, c, is horizontal; 

 1 the same when the arm is elevated ; and 3 when depressed, 

 in both these places the cell maintains its horizontal position. 

 4* 



