HOW TO FORM. 15 



Where a fall of water can be procured, as from a 

 cistern at the top of the house, a pipe may be 

 introduced at the bottom, and a fountain formed. 

 Secured in a glass case from the evil effects of smoke 

 and dry ness, a most charming vegetation with 

 a variety of aquatic plants and animals may be 

 secured in the midst of the poisonous atmosphere 

 of our cities and manufacturing towns. 



It must be confessed, however, that these glass 

 vessels have their defects. The rays of light, in 

 passing through their rounded sides, distort the 

 objects contained in them, and often give the 

 observer very indistinct notions of their form and 

 size. They are liable, also, to break, not only with 

 a slight blow, but even with a noise at a distance : 

 this is a very unhappy occurrence ; no one can con- 

 template without sorrow the treasures of weeks 

 and months of anxiety all scattered in an instant, 

 and perhaps the drawing-room table, with its books 

 and ornaments, saturated with water. Such acci- 

 dents lead us to think of tanks. The vessels to 

 which this term has been applied are made of sheet 

 glass ; they can be made of any size, and are not 

 only less liable to break, but the objects are seen 

 better through them. The jars admit too much 

 light for some things, but in the tank one or more 

 sides may be made of opaque materials, as slate. 

 It is hardly necessary, perhaps, to describe how 

 these tanks can be made ; they are now articles of 

 extensive manufacture, and a selection is kept for 

 choice in almost every establishment where glass is 

 sold. 



It will be found in most cases, in London, neces- 

 sary to have covers both for the jars and tanks ; 

 their principal object is to keep out the soot, 

 which is a fertile source of inconvenience in all 

 our large towns, and leads to the very injurious 



