MANUAL OF NATURAL HISTORY. 675 



them across the grain, to prevent their warping. 

 To equalize the pressure the heap must be divided 

 by thinner boards, of from a quarter to three-eighths 

 of an inch in thickness, inserted at intervals. On 

 the top of the whole a weight should be placed, 

 varying from 901bs. to 180lbs. When stationary for 

 a time, the most simple mode of applying pressure 

 is by means of stout duck or canvass bags contain- 

 ing sand, or fine gravel, which can be filled and 

 emptied at pleasure ; but while moving, the best 

 means of securing the parcel, and at the same press- 

 ing the plants, is by a rope run twice round the 

 boards and tightened by a rack-pin. 



11. A pair of botanical-forceps, or, where these 

 cannot be procured, a pair of surgeon's forceps with 

 rather fine points. 



12. A setting -needle, employed in spreading out 

 delicate plants, and especially Algce, easily made by 

 inserting a stout needle into a wooden handle : a 

 porcupine's bristle answers this purpose well. 



] 3. A small saw will frequently be serviceable 

 for cutting off portions of branches or sections of 

 small trunks for specimens. 



14. A small drag for searching the bottoms of 

 pools for fresh-water species ; this can be made 

 by fastening four or five stout fish-hooks together, 

 after the fashion of a boat's grapnel. 



15. Bottles and jars for preserving moist speci- 

 mens. The bottles we would recommend as well 

 adapted for such purposes are similar to those now 

 made for containing pickles, &c, with a rim around 



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