Page:Popular Science Monthly Volume 88.djvu/931

 Popular Science Monthly

��903

��A Strange Spongelike Rock

THE so-called sponge rocks near Livingston, Montana, have at- tracted the attention of many travelers and scientists on account of their re- markable tracery and porosity. They appear like huge pieces of pumice stone intricately carved by Nature into in- numerable cells, webs and cavelets. Some of the pieces are almost threadlike.

The rock is sandstone, which was formed millions and millions of years ago when the entire State of Montana was the bottom of a sea. In the course of ages, Montana has been bodily up- lifted several thousand feet.

The spongelike formation of the rock, as it appears to-day, is of course due to the wearing action of water and wind, the softer particles of the rock having been washed or blown away, leaving the harder portions standing. There are a number of these rocks in the same locality, and several of them are said to have been appropriated by wild bees and other insects.

����The spongelike appearance of this rock is due to the wearing action of wind and rain

��Take this portable dark-room with you in the woods and develop your negatives on the spot

A Portable Dark-Room for Photographers

A PORTABLE dark-cabinet has been invented, which does away with many inconveniences encountered by photographers in developing their nega- tives without the advantage of a suita- ble dark-room. A metal framework supports a table or shelf adjustable to any desired height. Extending above the table are two rods supporting a square frame to which is attached a large hood. This hood completely envelops the table and affords enough room for the upper portion of the photographer's body behind the table. A hole in one side of the covering is used for intro- ducing the materials in the cabinet. Another hole in its lower part is provided with a strap or elastic band, which passes around the waist of the operator as he enters the hood.

The cabinet is lighted by a window of ruby glass directly over the table and opposite the photographer. Eresh air is supplied by means of a mask with a rubber tube leading to the outside. Tourists who take many pictures can make'good use of this cabinet.

�� �