On the Entrance Passages in the Pyramids ofGiaeh. 133 



By the analysis it will be observed that the total amount of 

 iron as carbonate and peroxide is equivalent to about 45 per 

 cent. Comparing this with Mushet's black band (the richest 

 ore which is worked in England), we have, it is true, no great 

 preponderance in favour of the spathic carbonate, except in 

 the purity of the ore. In comparison, however, with the ores 

 usually employed in this country it possesses great advantages. 



Of 7 analyses of clay iron-stone from the Glasgow fields 

 the average in iron is 30 per cent. ; showing an advantage of 

 50 per cent, on the product to be obtained from this mineral. 



This, although avast recommendation, is perhaps the least 

 that can be urged in favour of this valuable ore. The ease 

 with which it would be worked is another subject of consi- 

 derable importance. A simple reduction with carbonaceous 

 matter is probably all that would be required, there being little 

 or no impurities which would call for a flux to remove them. 



But the remarkable purity of the mineral is that which' as a 

 source of iron would principally constitute its value, and 

 would fit it eminently for the production of the best varieties 

 of that substance, and would enable it to rival successfully the 

 Swedish ore in this especial application of iron. 



I regret exceedingly my inability to supply more tangible 

 information as to the extent and locality of this ore, and its 

 relations to the coal strata, which must materially affect its 

 value ; but repeated attempts to obtain this information have 

 proved abortive, I presume, from the existence of a jealousy 

 on the part of the proprietors to divulge it. 



It is well however that the attention of mineralogists should 

 be drawn to the subject, as it is by no means improbable that 

 spathic iron ore may exist in other localities to an equally 

 large extent. 



XX. Remarks on Sir John F. W. Herschel's Observations on 

 the Entraiice Passages in the Pyramids of Gizeh. By a 

 Correspondent. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



THE arguments brought forward by Sir J. Herschel in his 

 " Observations on the Entrance Passages in the Pyra- 

 mids" (reprinted in No. 162 of the Phil. Mag., S. 3. vol.xxiv. 

 p. 481, from Colonel Vyse's work on the Operations carried 

 on at the Pyramids of Gizeh in 1837), prove pretty satisfacto- 

 rily that the inclined passages there alluded to were designed 

 for astronomical purposes, though the principal and almost 

 fatal objection to such an hypothesis, namely, that the en- 

 trances to these tunnels or passages were carefully and se- 



