186 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE. 



buildings in Rome, London, &c., views of shipping, land- 

 scape views, &c., to the number of one hundred and 

 upwards, may be obtained with the instrument, for the low 

 price of eight cents each, which is not one half the price 

 usually charged. 



Price, diagonal print glass with 4 inch lens, $2.75. 



5 $3.25. 



" " " " " 6 ' " $3.75. 



" prints, 14 by 22 inch, per dozen, $1.00. 



" " " hundred, $8.00. 



The Portable Camera Obscura. (Fig. 702.) This con- 

 sists of a box usually about twelve inches long, having one 

 end attached to a movable slide, which may be drawn out 

 a few inches, in which is fixed a convex lens, of a suitable 

 focus ; within the box is placed diagonally a mirror, so as 

 to reflect the object on a ground glass, occupying nearly 

 half of the top of the box, and over which is hinged a 

 screen or shutter having closed sides, moving within the 

 sides of the box to exclude the external light ; on the rough 

 glass external objects are beautifully represented, affording 

 a pleasing amusement to young persons, as representing a 

 moving panorama of animated nature. 



Fig. 702. 



Directions for Use. Place on the ground glass a piece of 

 good tracing paper, and present the instrument to the object 

 to be copied, which should be strongly illuminated. The 

 camera should be placed level. Draw the slide till the ob- 

 ject is reflected on the paper, and if the lines are followed 

 with a pencil, a correct copy of the view will be obtained. 

 If a portrait be desired, the person should be placed in the 



