INFUSORIAL, ANIMALCULES. 25 



hook at the end of it, and a piece of twine, should always 

 form part of the equipment. As the margin of small 

 ponds is sometimes difficult of near approach, I have 

 contrived a spring-hook, which is attached to a moveable 

 ferule, and made to fasten to the end of the walking-stick. 

 This lays hold of the neck of the phial, and enables you to 

 charge it from the surface of the water, in the immediate 

 vicinity of the stalks of water-plants, a situation generally 

 abounding with Infusoria. Take with you, also, a pocket 

 magnifier, of shallow power. This may be mounted in 

 various ways ; but the one I prefer is the triple, having 

 the lenses arranged in the same plane ; the convenience of 

 which is, that you will have three different powers always 

 ready for use, without the necessity of moving them ; and 

 that, the mounting being flat, it will be very suitable for 

 the waistcoat pocket. Sling this, with a piece of ribbon, 

 about the neck, and there will be no danger of losing it. 

 The magnifying powers usually selected are those from 

 five to fifty diameters ; the first, or largest, serving to 

 distinguish the masses; the intermediate, to show the 

 genera] movements, so as to determine pretty nearly 

 whether the water you have collected is worth retaining or 

 not ; and the smallest, or most powerful, for examining the 

 contents with more minuteness. This latter power will 

 not so frequently be called into use abroad as at home ; 

 because, with a little practice, the middle and shallow 

 powers will be found to answer every purpose. 



Having now mentioned all the needful apparatus, 

 proceed to the nearest ponds of water in the neighbour- 

 hood, and should there be healthy Lemnse on their surface, 

 or Confervee, or other aquatic plants, you will be almost 



