68 ANNUAL OF SCIENTIFIC DISCOVERY. 



measures made of tinned iron, the larger one for the acid powder 

 and the smaller one for the alkali, are employed. When bread 

 is required to be made, every pound of Hour is mixed with a 

 measure of the aeid powder and a measure of the alkali powder, 

 and sufiieient water added to make dough, which is presently 

 made into loaves and baked. In one and a half to two hours 

 bread may be made by this })rocess. The chemical change 

 which takes place will be easily intelligible ; carbonic acid is gen- 

 orated and phosphate of tiie alkali is formed at the same time. 

 Tiie essential feature in llorsford's invention is the economical 

 getting of phosphoric acid in the shape of a dry, white powder. 

 This is done by taking bones, burning them, and then treating 

 the well-burnt bone-earth (which consists of phosphate of lime 

 and magnesia) with a certain quantity of sulphuric acid, so as to 

 remove two-thirds of the lime, and leave a soluble superphos- 

 phate of lime. The sulphate of lime which results from the action 

 of the sulphuric acid is separated from the rest b}' lilLration, and 

 the solution subsequently concentrated bj- evaporation, and, when 

 it becomes very concentrated, mixed with a certain quantit}' of 

 flour, and dried up. The mixture of flour with the superphos- 

 phate admits of being reduced to the linest powder, and consti- 

 tutes the acid powder just referred to. It will be observed that 

 the alkali powder contains soda, whereas potash is required, in 

 order to furnish the right kind of mineral salts. Liebig proposes 

 to rectify this defect by using a certain quantity of chloride of 

 potassium along with the alkali. Chloride of potassium is now 

 tolerably cheap, owing to the finding of immense quantities of it 

 at Stassfurt. — British Medical Journal. 



TELEICONOGRAPHY. 



M. Revoil, an architect well known in France, from having the 

 charge of the restoration of the Roman remains at Montpellier, 

 Toulan, Nimes, has recently been engaged in a special study of 

 the early architecture of the southern provinces of the ancient 

 kingdom. In the course of his attempts to arrive at exactitude 

 of definition, by the aid, at one time, of the camera lucida, and 

 at another, of the telescope, he has been induced to make experi- 

 ments as to the combination of the j)rinciples of tlie two instru- 

 ments. The result of this effort M. Revoil has called the TiUi- 

 conograph. 



The principle of this instrument is that of allowing the image 

 transmitted by the object-glass of a telescope to pass through a 

 prism connected with the eye-piece. The rays of light that 

 would, in the ordinary' use of the telescope, be transmitted direct 

 to the eye, are refracted b}' this prism, and thrown down upon a 

 table placed below the eye-piece. The distance between the 

 prism and the table determines the size of the image projected 

 on the latter, and it is easy for tLe observer to trace on a paper 

 placed on this sketching-table the actual outlines indicated by 

 the refracted light. 



The idea once grasped, it is easy to work out the details. The 



