This page has been validated.
PLATE VII.
168
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/69/An_Elementary_Treatise_on_Optics_image_168.png/150px-An_Elementary_Treatise_on_Optics_image_168.png)
169
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/3/3b/An_Elementary_Treatise_on_Optics_image_169.png/150px-An_Elementary_Treatise_on_Optics_image_169.png)
170
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/1/16/An_Elementary_Treatise_on_Optics_image_170.png/150px-An_Elementary_Treatise_on_Optics_image_170.png)
171
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/9/9f/An_Elementary_Treatise_on_Optics_image_171.png/150px-An_Elementary_Treatise_on_Optics_image_171.png)
172
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/e/ee/An_Elementary_Treatise_on_Optics_image_172.png/150px-An_Elementary_Treatise_on_Optics_image_172.png)
173
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/f/f1/An_Elementary_Treatise_on_Optics_image_173.png/150px-An_Elementary_Treatise_on_Optics_image_173.png)
174
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/a/a3/An_Elementary_Treatise_on_Optics_image_174.png/150px-An_Elementary_Treatise_on_Optics_image_174.png)
175
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/An_Elementary_Treatise_on_Optics_image_175.png/150px-An_Elementary_Treatise_on_Optics_image_175.png)
176
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/1/14/An_Elementary_Treatise_on_Optics_image_176.png/150px-An_Elementary_Treatise_on_Optics_image_176.png)
177
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/5/52/An_Elementary_Treatise_on_Optics_image_177.png/150px-An_Elementary_Treatise_on_Optics_image_177.png)
178
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/6c/An_Elementary_Treatise_on_Optics_image_178.png/150px-An_Elementary_Treatise_on_Optics_image_178.png)
179
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/An_Elementary_Treatise_on_Optics_image_179.png/150px-An_Elementary_Treatise_on_Optics_image_179.png)
180
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/67/An_Elementary_Treatise_on_Optics_image_180.png/150px-An_Elementary_Treatise_on_Optics_image_180.png)
181
[return]
![](http://upload.wikimedia.org/wikipedia/commons/6/68/An_Elementary_Treatise_on_Optics_image_181.png)
182
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/f/fe/An_Elementary_Treatise_on_Optics_image_182.png/150px-An_Elementary_Treatise_on_Optics_image_182.png)
183
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/f/ff/An_Elementary_Treatise_on_Optics_image_183.png/150px-An_Elementary_Treatise_on_Optics_image_183.png)
184
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/00/An_Elementary_Treatise_on_Optics_image_184.png/150px-An_Elementary_Treatise_on_Optics_image_184.png)
185
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/01/An_Elementary_Treatise_on_Optics_image_185.png/150px-An_Elementary_Treatise_on_Optics_image_185.png)
186
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/f/ff/An_Elementary_Treatise_on_Optics_image_186.png/150px-An_Elementary_Treatise_on_Optics_image_186.png)
187
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/63/An_Elementary_Treatise_on_Optics_image_187.png/150px-An_Elementary_Treatise_on_Optics_image_187.png)
188
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/5/5a/An_Elementary_Treatise_on_Optics_image_188.png/150px-An_Elementary_Treatise_on_Optics_image_188.png)
189
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/b/b4/An_Elementary_Treatise_on_Optics_image_189.png/150px-An_Elementary_Treatise_on_Optics_image_189.png)
190
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/4/40/An_Elementary_Treatise_on_Optics_image_190.png/150px-An_Elementary_Treatise_on_Optics_image_190.png)
191
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/d/d3/An_Elementary_Treatise_on_Optics_image_191.png/150px-An_Elementary_Treatise_on_Optics_image_191.png)
192
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/4/4e/An_Elementary_Treatise_on_Optics_image_192.png/150px-An_Elementary_Treatise_on_Optics_image_192.png)
193
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/8/88/An_Elementary_Treatise_on_Optics_image_193.png/150px-An_Elementary_Treatise_on_Optics_image_193.png)
194
[return]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/c/ce/An_Elementary_Treatise_on_Optics_image_194.png/150px-An_Elementary_Treatise_on_Optics_image_194.png)