snow; in spring, a brown to enable them to hide in weeds, rocks, etc.) 



There are muscles under the skin by which birds can raise their 

 feathers. Some of these are strong as in the crests of some birds, and in 

 the tails of turkeys and peafowls which have the habit of struting. 



If the feathers be removed from the bird and the naked skin observed 

 it will be found that the feathers have a very different arrangement. 

 The arrangement diifers in different kinds of birds. There are naked 

 patches, and patches covered with feathers and in the latter the feathers 

 are arranged in rows. In some forms this definite arrangement is not so 

 distinct as in ducks, chickens and our common birds. The children may 

 from time to time compare forms. 



Note. — These lessons on feathers may serve as suggestions for lessons 

 on the coverings of other animals. 



Oxygen. 



The air contains constantly oxygen, nitrogen, argon, carbonic acid, 

 and vapor of water. The first two make up the main bulk of the air, 

 the last three are very small in amount. We wish to study each of these 

 gases, except argon, a recently discovered one, which in this work we 

 cannot make or isolate. Oxygen can be made and studied with very 

 little apparatus. 



The materials used ax& potassium chlorate and black oxide of manga- 

 nese. The potassium chlorate gives up the oxygen it contains very read- 

 ily on heating. In fact it is liable to give off such a large quantity of 

 gas at once, that there is an explosion. Consequently we mix with it, 

 the black oxide of manganese which seems to retard the giving off of 

 the oxygen. 



Mix well equal amounts of the two substances. A test tube one-third 

 full will make sufficient gas for the work. Fit the test tube with an air 

 tight cork, and a glass tube to carry off the gas. To catch the gas, have 

 ready at least five wide-mouthed bottles (8 to 15 oz. in size). These are 

 filled with water and inverted in a pan of water. The delivery tube 

 carrying the gas from the test tube is bent so that it can be made to con- 

 veniently reach under the mouth of an inverted bottle. When all is 

 ready with the alcohol lamp, heat the potassium chlorate and black 

 oxide of manganese mixture and the gas will rapidly come away and 

 bubble up into the inverted bottles, displacing the water and filling the 

 bottle. Then another bottle is brought over and so on, till all are filled 

 or the oxgen gives out. 



In beginning to apply the heat, do so at first gently and to the upper 

 part of the test tube. This will heat the tube, and prevent moisture 

 forming on it later and breaking the tube. Next heat the upper part of 

 the potassium chlorate mixture, first exhausting its oxygen, then work 

 downwards. If you begin at the bottom of the mixture, as the gas 

 comes oflF, it is liable to puff the black dust up and choke the delivery 



