550 KEPORT — 1880. 



cisely similar results with reagents, and also that the same kind of ink made hy 

 the same maker at different times gives different residts. 



Lastly, persons treat and use inks so differently that although two persons may 

 he supplied with precisely the same ink, yet when it has been in use by them for 

 some time, the character of each may become diti'erent, being altered by the user 

 leaving his steel pen in the ink, or by leaving it exposed to the light, or by tilling 

 the bottle up with one kind of ink before another kind has been entirely tinished, 

 or by mixing with it fluids such as water, beer, wine, &c., when the ink is nearly 

 dried up. Thus, as most people have in their ink-bottles fluids which are very 

 characteristic, the testing of the ink on papers or documents to discover the writer 

 may become of the highest importance, although it is seldom that this mode of in- 

 vestigation is adopted. 



6. Note on Silver Sulphate. By Philip Beaham, F.C.S. 



The silver sulphate was shown as brilliant transparent crystals of regular octahe- 

 dral shape and of higli refractive power. They were produced hj pouring strong sul- 

 phmic acid on a plate of sUver, and adding a few drops of nitric acid. At first there 

 was a slight chemical action, bubbles of gas being liberated. In a day or two the 

 whole of the sulphuric acid acqiures a deep purple tint, probably due to the for- 

 mation of some oxide of nitrogen. After a lapse of two to three weeks the purple 

 tint sinks towards the silver, and a slight brown tint can be seen on the surface, 

 the layer of liquid above the silver being colourless. About this period long crj'stals 

 form, which re-dissolve, and the liquid becomes colourless. In the course of a few 

 days brilliant specks are seen, which develop into perfect crystals ; those shown 

 had taken over six months in forming. 



6. The Effects of Magnesia on Vegetatimi. By Major-General Scott, 



C.B., F.E.S. 



Not among the least wonderful of the anomalies in the conduct of human beings 

 is the persistence, in opposition even to their own interests, with which they adhere 

 to a prejudice long after it has been overturned by experience. The erroneous 

 views of the effects of magnesia on vegetation afford a notable instance. Eminent 

 cultivators have given their testimony from actual practice of its favourable effects, 

 yet the prejudice continues so strong that farmers will often carry other limes 

 from a long distance, and at a much greater cost, rather than employ those made 

 from dolomite. Its slower absorption of carbonic acid, or some defect in the mode 

 of using it, had given in tlie first instance an unfavourable impression regarding 

 magnesian lime, and this impression has been handed down from one author to 

 another, and has been accepted by the unthinking agriculturist without question. 

 Instances occur even in which men of science have contributed to the propagation 

 of the error. 



Now and again there has been some slight protest against the assumption that 

 magnesian lime had qualities noxious to vegetation, but these protests have pro- 

 duced little effect, and the substance, though known to be an important constituent 

 of plants, has seldom been made a component of manures. Thus Professor Johnston 

 recommends the making of experiments both with caustic and mild or carbonate of 

 magnesia, and states, in 1849, that, ' in consequence of previous recommendations 

 it (carbonate of magnesia) has been tried in numerous experiments by Mr. Gardner 

 at Barochan in Renfrewshire, and by Mr. Main at Whitehill in Midlothian. This 

 was never applied alone by these gentlemen, but always as an ingredient of mixed 

 manures, in which it formed only a small proportion. These experiments, there- 

 fore, throw no light upon the special effects of this substance on our different crops 

 and soils.' 



Thirty years after this we stiU find Mr. Jamieson thus writing in the report of 

 the proceedmgs of the Aberdeenshire Agricultural Association for 1878. Speaking 



