180 ANNUAL OF SCIENTIFIC DISCOVERY. 



such as are seen during the combustion of iron in oxygen gas, and 

 while in a fluid state they assume a spheroidal form. They are 

 carried by the draught into the flue, and, being of greater specific 

 gravity than the carbonaceous matter forming the smoke, they fall 

 before the current of air has reached the chimney. Some of the 

 dust has been a considerable time in the flue, exposed to the in- 

 tensely heated circulating flame ; the reducing action of this would 

 probably convert some of the oxide into metallic iron. Many of 

 these balls have the appearance of reduced oxides. The flue dust 

 contains a larger amount of ferruginous matter than can be ac- 

 counted for by the analysis of coal ash. I think the surplus may 

 be regarded as representing the wear and tear of the iron work 

 about the furnace, such as fire-bars, boiler-plates, etc. The brick- 

 work and cement about the boiler and flues may also supply some 

 of the silica, alumina, and iron for these balls, numbers of which 

 are merely thin shells. The movements of these objects, caused 

 by the approach of a magnet under the stage of the microscope, 

 are somewhat amusing, and it is at times startling to see the crys- 

 talline objects, both spherical and irregular, exhibit magnetic at- 

 traction ; probably they contain particles of iron imbedded in 

 them ; if they do not, may we not imagine that there is some mag- 

 netic compound in which the crystalline matter predominates? 

 When we consider the accidental condition under which this mat- 

 ter has combined, it is just possible that some new molecular ar- 

 rangement or combination of elements may have taken place. It 

 is very probable that many of these polished balls are much more 

 complex in their elementaiy constitution than I have stated. They 

 are, in fact, a kind of glass, and many of them merely bulbs. 

 Pelouze states that glass is probably an indefinite mixture of 

 definite silicates. Glass, containing small quantities of ferrous 

 oxides and sodic sulphates, when exposed to sunlight, becomes 

 yellow, and possibly some of these balls may have changed in 

 color since they came from the flue. H}'drochloric and nitric acid 

 exert very little action on the ferruginous globes ; this may be due 

 in some measure to the high temperature at which the oxides have 

 been formed ; in other cases they are no doubt protected by an 

 external coating of some silicate. It would require much time 

 and patience to collect a sufficient number of each kind of these 

 minute objects for a chemical analysis ; but the spectroscope might 

 probably assist in revealing their constitution. J. B. Dancer. 



THE TAR ACIDS CARBOLIC AND CRESYLIC ACIDS. 



Mr. William Crookes, F.R.S., who was appointed by Her Bri- 

 tannic Majesty's commissioners, charged with investigating the 

 history, nature, and remedy of the cattle plague that has recently 

 caused such havoc among the herds of England, to make a thor- 

 ough examination of the disease, furnished to the commissioners 

 a valuable report, from which the following* is an extract: 



" These two bodies are so commonly known under the name of 

 acids, that I shall continue so to designate them, although by 

 chemists they are more; generally classed with the alcohols. '"They 



