244 ANNUAL OF SCIENTIFIC DISCOVERY. 



water. Becurring to the composition of guano-rock, we see that the propor- 

 tion of organic salts and other organic matter, is much larger than exists hi 

 the guano from which it was derived. The physical characters of the rock 

 are modified by the presence of these compounds, but the most remarkable 

 change is that from a granular to a compact solid. This change could be 

 effected by infiltration, as takes place from calcareous waters ; but as the 

 rock guano is above the mass producing the soluble organic salts, it is neces- 

 sary to consider another condition. When water holding saline matter in 

 solution evaporates from the surface of the earth, pure water alone escapes, 

 while the saline and colored organic compounds remain at or near the surface. 

 In accordance with this law, the saline matters which can be dissolved, and 

 the colored matters which can be suspended, in water, rise to the surface, 

 and so long as capillarity can act, they are .deposited in the porous parts, 

 gradually filling the pores and consolidating the surface. Doubtless, while 

 this process is proceeding, rains carry back a part, which is to be raised anew, 

 until finally the surface rock, no longer pervious, becomes cemented into the 

 compact state it now presents, by this action of capillarity. As the material 

 of the guano-rock has been organized at one time, and may now be consider- 

 ed as mineralized, the specimens present a fine illustration of the action of the 

 minor natural forces in changing the physical conditions of matter, as well as 

 its ch^Tiieal composition. On the other hand, the putrefaction of fish remains, 

 being often accompanied by the formation of acids, we are able to trace to 

 their sources the organic salts of lime, as well as the phosphate of lime, which 

 analyses show to exist in sea-water. 



ON THE PREVENTION OF THE OXIDATION OF METALS. 



Those familiar with electrical science are well acquainted with the fact 

 that zinc exercises positive relations with regard to most other metals. In 

 other words, it possesses the power of keeping them in a negative state when 

 in contact with them. In this negative state they are incapable of entering 

 into combination with oxygen, and this circumstance may be applied with 

 much advantage to the prevention of the oxidation of machinery, especially 

 such parts of it as, in the case of marine engines, are liable to come in contact 

 with water. Many instances will at once suggest themselves, in which 

 much manual labor might be saved by the simple contrivance of appending 

 either a ring or a slip of zinc to the metal to be preserved bright. It would 

 be especially applicable in the case of bayonets and rule barrels ; and a zinc 

 edging to a scabbard would prevent rusting of the sword. 



THE MANUFACTURE OF ALLOTS, OR COMBINATIONS OF METALS. 



It is a curious but nevertheless undeniable fact, that no kind of manufacture 

 has received less benefit from the recent progress of chemical knowledge in 

 this country than the fabrication of alloys. This is all the more surprising, 

 when we consider the enormous field open tp inquiry, and the richness of 

 the harvest to be there gathered. A new alloy is really a new metal given 

 to society ; and although the apathy of scientific men with respect to the sub- 

 ject has hitherto led to the production of very few such metals, yet more than 



