Agriculture. — On Spring Pasture. 355 



ble one, from a weaker, arsenical solution. Coffee was then 

 added to the sohition of copper and of carbonate of potash, 

 but without arsenic, and the effect resembled that of the 

 stronger arsenical solution, more than this last was resembled 

 by that of the weaker. 



But the most important facts mentioned by Dr. Porter 

 remain still to be stated. He found, that, — in the production 

 of Scheele's green, by arsenic, sulphate of copper and car- 

 bonate of potash, — chromate of potash might be substituted 

 for the arsenic ; and that it produced a precipitate not to be 

 distinguished, by the eye, from Scheele's green. He ascer- 

 tained, also, that even Mr. Hume's celebrated test, nitrate 

 of silver, (as modified in its application by Dr. Marcet,) 

 gave, with chromate of potash, a yellow precipitate; which, 

 when placed side by side with one produced by arsenic, 

 could not be distinguished by their colour and appearance. 

 Dr. Porter's experiments appear, then, to throw still greater 

 suspicion on the infalhbility of tests for arsenic, and are 

 worthy of being repeated.* His results were exhibited to us. 



* The nitrate of silver used by Dr. Porter, was the lunar caustic dissolved, 

 and the chromate of potash contained an excess of alkali, having been formed 

 by heating potash on chromate of iron. 



AGRICULTURE. 



Art. XIX. — On Spring Pasture; by Professor Eli Ives. 



A PLANT which will grow in the autumn, of a size suf- 

 ficient to make it an article of food for cattle, and which 

 will not be destroyed by our severe winters, is much need- 

 ed by the farmers in the northern and eastern states. 

 The severity of the weather in January, and the sudden 

 transitions of the temperature in March and April, are 

 equally unfavourable to vegetation. All the grasses occa- 

 sionally, and at least the foliage and the roots of many, are 

 destroyed by the severity of the winter and spring. 



The burnet (poterium sanguisorba) has been recom- 

 mended to be cultivated for early spring pasture. Objec- 

 tions exist against cultivating the burnet for this purpose. 

 In the first place, it requires the whole of the previous sum- 



