Foreign Literature and Science. 186 



in photometrical observations, screens should be used which 

 are not very smooth, and the shadows should be brought 

 near each other ; and even so as to allow their borders to 

 touch. — Ferrusac's Bull. Oct. 1827. 



32. Impurity of rain water. — In evaporating thirty ounces 

 of rain water every month, which at the end of the year 

 amounted to three hundred and sixty ounces, M. Brandes 

 obtained a total residuum of 2.75 grains. It was composed 

 of resin, pyrrhin, (a vegeto-animal substance,) mucus, hydro- 

 chlorate, sulphate and carbonate of magnesia, hydro-chlo- 

 rate of soda, sulphate and carbonate of lime, hydro-chlorate 

 of potash, oxide of iron and manganese, and an ammoniacal 

 salt. — Ihid. 



33. Sulphur in assafoetida. — In treating assafoetida with 

 caustic potash, and adding an acid to the solution, efferves- 

 cence is produced, and a gas disengaged which colors paper 

 of acetate of lead like sulphuretted hydrogen. 



If an alcoholic solution of assafoetida be evaporated, and 

 the residuum be treated with aqua regia, a liquid is produced 

 which contains sulphuric acid. 



In burning the volatile oil of assafoetida in a pure state, a 

 very strong odor of sulphurous acid is developed. This oil, 

 heated to redness with potash, produces a mixture of char- 

 coal and sulphuret of potash. M. Zeise presumes that his 

 ulterior researches will enable him to discover sulphur in a 

 great number of organic substances. It may be remember- 

 ed also that M. Planche has already detected the presence of 

 sulphur in the umbellifera. — Ibid. 



34. Incompatible salts. — M. Brandes has demonstrated 

 by means of an artificial mineral water, that the waters of 

 Pyrmont contain carbonate of soda and sulphate of lime, 

 and not, as has been pretended, sulphate of soda and car- 

 bonate of hme ; because if these latter salts co-exist, even 

 in a large quantity of water, a material decomposition takes 

 place. — Ibid. 



33. Steam Engines in Great Britain. — It is confidently 

 asserted that there are now in Great Britain, fifteen thousand 

 steam engines. Some of them are of prodigious size. In 

 the county of Cornwall, for example, there are some of the 



Vol. XV,— No. I. 24 



