826 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



the sun is capable of furnishing heat to our planet for at least 30,- 

 000,000 of years. 



Picture of a Podura Scale. 

 A photograph of a Podura scale has recently been made by Mr. 

 Curtis, of Washington, under the direction of Major Woodward, 

 with the aid of a microscope having a power of more than 1,000 

 diameters. The quill-like markings on the surface were splen- 

 didly rendered. This photograph was warmly commended at the 

 last meeting of the American Photographical Society. 



A Photographic Wonder. 

 The photographic process is now brought to such perfection 

 that it can produce a picture of a projectile the instant it leaves 

 the mouth of a gun, and before the recoil has taken place. The 

 most sensitive collodion must be used to effect this, and in order 

 to have the exposure only at the instant required, the charge in 

 the o"un is ignited by a galvanic battery. This is done by having 

 a small portion of the conducting w^ire of platinum which is placed 

 in contact with the powder. When the electric current is sent 

 throuo-h the wire the platinum becomes red hot and ignites the 

 powder. This very current is s«nt through a coil of wire around 

 a core of soft iron, which thus becomes a magnet and lifts the disk 

 in front of the lens. Yet the instant the platinum melts the cur- 

 rent ceases, and the iron core being demagnetized can no longer 

 hold up the disk. Thus, in much less time than it could be 

 eftected by the human hand, the plate is exposed and covered; 

 besides the exposure takes place at the precise instant required. 



Solidified Extract of Oyster. 

 * This is the designation of a new form of food for which patents 

 have lately been granted to a gentleman in this city. The extract 

 is made from the natural liquor or juice of the oyster reduced to 

 a state of dryness by evaporation in vacuo. It is designed chiefly 

 for the production of soup, luit may be used for enriching other 

 aoups, gravies, etc. Being in the form of a coarse powder and 

 packed in tin cans or bottles it remains unchanged so long as kept 

 dry, is easily dissolved and convenient to use. The contents of a 

 can containing twelve ounces will make, without other addition, 

 except salt, pepper, and the requisite proportion of water, 100 

 dishes of nutritious, well flavored oyster soup, and at a cost of 

 material not exceeding two cents a dish. A man on an overland 



