12 SOME HINTS ON THE PREPARATION AND 



diameter of the covering glass and the thickness of the object. In 

 mounting our present specimens, say with covers of 5/6 inch diam- 

 eter, it will be found that more of the balsam will be required to fill 

 up evenly to the edge of the cover, with one of the legs than 

 with a wing. The great aim should be to get exactly the right 

 amount dropped on the slide at first, so that it will fill to the edge 

 of the cover when the latter is pressed down, without any excess 

 exuding, or any additional filling being required. No rule can be 

 given for doing this; only continuous practice can give one the 

 necessary skill ; but it is worth trying for, since a mount thus made 

 possesses an artistic appearance, which cannot be equalled by any 



p. Drying Oven. 



other means. The drop of balsam having been placed 

 in the centre of the slide, the wing is taken from the benzole 

 with the forceps, and thrust into it the balsam gently, but 

 firmly ; and then with one of the needles it is to be pushed down 

 upon the slide, (into firm contact with its surface, in fact), and ar- 

 ranged in proper position. Now mark this point carefully. If the 

 object be left suspended in the drop of balsam, as soon as the cov- 

 ering glass is applied, it will float out of position, and much valuable 



