ing the constituent parts of this ore, both analytically and syntheti-
cally. In the progress of this inquiry, a certain analogy soon pre-
sented itself, between these compounds of sulphur and iron and
those of other inflammable substances, such as carbon and phospho-
rus, with the same metal, which suggested the idea of some experi-
ments on the subject; from whence various facts were deduced, not
only of much curiosity, but also likely to lead to some useful pur-
poses. as will appear hereafter. The principal results of this labo-
rious investigation are,—
1. That the component ingredients of the magnetical pyrites are sulphur, and iron in the metallic state, the former being to the latter in the proportion nearly of 37 to 63.
2. That the chemical and other properties of this substance are very different from those of the common martial pyrita; which, however, are likewise composed of sulphur and iron, but varying in proportion from between 52 to 54 of sulphur, and 48 to 46 of me- tallic iron. Whence it appears, that the relative proportions in the composition of the magnetical pyrites, and of the mean of the com- mon pyrites, is between 16 and 17.
3. That as the magnetical pyrites agrees in analytical results, as well as in all chemical and other properties, with that sulphuret of iron which hitherto has been only known as an artificial product, there is no doubt that it is identically the same, and that its pro- portions are probably subjected to a certain law, which, under cer- tain circumstances, may be supposed to act in an almost invariable manner.
4. That in the formation of the common martial pyrites, there is a deviation from this law, and that sulphur becomes a predominant ingredient, variable in quantity, but which, by the present experi- ments, has not been found to exceed between 54 and 55 per cent. ; a proportion, however, which possibly may be surpassed in other pyrites which have not as yet been chemically examined.
5. That iron, when combined naturally or artificially with 36 or 37 per cent. of sulphur, is not only still capable of receiving the mag- netic fluid, but it is also rendered capable of retaining it, so as to become in every respect a complete magnet. And the same may in a great measure be inferred respecting iron which has been arti- ficially combined with 45-;- per cent. of sulphur.
6. That beyond this proportion of 45% per cent. of sulphur, (at least in the natural common pyrites.) all susceptibility in iron of the magnetic influence appears to be destroyed; and although the pre- cise maximum, which is capable of producing this effect, has not as yet been determined by actual experiment, it is certain that the limits are between 45 and 52 ; unless some alteration has taken place in the state of the sulphur or iron in the common martial py- rites, different from' that which is conceived according to the present state of chemical knowledge.
7. That as carbon, when combined in a certain proportion with iron (forming steel), enables it to become a permanent magnet, and
