Miscellanies. 363 



per being then of different shades of green. In this way also the 

 object may be represented of a darker shade than the ground. 



Paper prepared with bichromate of potash is equally sensitive with 

 most of the papers prepared with salts of silver, though inferior to 

 some of them. It is not sufficiently sensitive for the camera obscura, 

 but answers quite well for taking drawings from dried plants, or for 

 copying prints, &c. Its great recommendation is its cheapness and 

 the faciHty with which it can be prepared. The price of the bichro- 

 mate of potash is 2s. 6d. per lb., whereas of the nitrate of silver only 

 half an ounce can be obtained for that sum- The preparing of paper 

 with the salts of silver is a work of extreme nicely, whereas both 

 the preparing of the paper with the bichromate of potash and the 

 subsequent fixing of the images are matters of great simplicity, and 

 I am therefore hopeful that this method may be found of considerable 

 practical utility in aiding the operations of the lithographer, — Jamc- 

 sovPs Journal^ April to July — 1839. 



Edinburgh, 18, May, 1830. 



35. Fossil-Tree at Granton, near Edinhurglu — A great fossil-tree 

 similar to that at Craigleith, has been discovered in the sandstone 

 quarry at Granton. Its dimensions cannot yet be ascertained, but 

 the distance between the extreme points already uncovered is about 

 forty five feet, and its breadth, where most exposed, is about three 

 feet. — lb* 



- 



36. Notice upon tie Alcoholic Strength of Wines ; by Dr. Chris- 



xisoN. Various accounts have been given of the alcoholic strength 



of wines by Mr- Brande, Julia-Fontenelle, and others. The author 

 has been engaged for some time in experiments for determining the 

 proportion of alcohol contained in various wines of commerce, and 

 also the circumstances which occasion a variety in this respect. TIjc 

 present paper is an interim notice of the results. 



The method of analysis consisted in the mode of distillation, which 

 was applied with such contrivances for accuracy that nearly the 

 whole spirit and water was distilled over without a trace of empy- 

 reuma, and without the loss of more than between two and six grains 

 in 2000. From the quantity and density of the spirit, the weight of 

 absolute alcohol of the density 793.9, as well the volume of proof 

 spirit of the density 920, was calculated from the tables of Richter 



founded on those of Gilpin. 



The author has been led to the general conclusion that the alcoholic 

 strength of many wines has been overrated by some experimentalists, 

 and gives the following table as the result of the investigations he 

 has hitherto conducted. The first column gives the per-centage of 



