82 The Nature-Study Exhibition 



in its natural surroundings being the only subject of value or edification 

 as a study ". 



Another society, namely, that for The Protection of Birds, 

 was represented, and exhibited with the following objects, 

 to wit: 



"To acquaint teachers and others with the various ways in which 

 they will find the Society a useful ally in promoting Nature-study. The 

 primary intention of the society being to encourage the study of wild 

 bird life and the preservation and protection of our birds, among children 

 as well as adults, the co-operation of teachers is especially welcomed. 

 Many of its publications are adapted for school use, and deal with the 

 habits and utility of birds, while discountenancing wanton slaughter and 

 profitless collecting. The lantern slides exhibited are specimens from 

 the Society's collection of over six hundred, from which selections for 

 the illustration of lectures may be borrowed by any associate member, or 

 by any school or natural history club affiliated with the Society." 



An exhibit of a suggestive nature may be somewhat fully 

 considered. It consisted of a description by Mr. Sibert 

 Saunders, of Whitstable, of marine aquaria which can be 

 maintained without circulation or change of water. Striking 

 photographs were sent as illustrations. 



"These aquaria have been in operation for many years without 

 change of water, through careful attention to the law that growing vege- 

 tation, produced and maintained by the action of light, absorbs the car- 

 bonic acid gas given off by the animals, appropriates the carbon to its 

 own use, and gives off a fresh supply of oxygen for that of the animal 

 organisms which must, of course, be proportional to the bulk of water 

 in which they are kept." 



The hints as to formation and management drawn up by 

 Mr. Saunders are given below: 



" The Tank may be of any size, but must combine a large surface 

 area with a comparatively small depth of water. A serviceable tank of 

 small size would be about 24 inches long, 16 inches broad, and 7 inches 

 deep. Larger tanks may be of greater depth, but should have a false 

 bottom of slate, sloping from the front, and resting against the back at a 

 point a few inches from the top. Rock-work being arranged on this, the 



