[^24] 
A Letter from Dublin to the Publiftier of theft 
Trails , concerning the Porphyry Pillars in E- 
SIR,. 
YOii engage me after a very undeniable manner, as I 
perceive by the minutes of your Philofophical Soci- 
ety, to fend you fome Account of the Porphyry Pillars 
in E.gypt : And though I could have fatisfied your Curi- 
ofity much better in this matter, had vou thought of it 
when I was amongft my Papers in Oxford., yet rather 
than hazard your good Opinion, or give the leaft pre- 
tence of difrefpedl to your worthy Company, for whofe 
perfons and defigns I have fo juft an efteem and venerati- 
on : I here fend, not what's fit forme to write, or you 
to read but what I can remember upon this fubje^t. 
Nor do I intend to fpeak concerning the nature or 
compofition of ftones in general, or of Porphyry more 
particularly: But meerly as to matter of Fad, fo far 
chiefly as it fell under my own Cognifance, i. e, if you 
pleafe, rather like an Hifiorian thzn 2i Thilofopher, 
In the firft place then, I think it may betaken for 
granted, that there is nofuch ^arry, or Rockof ftone 
father, in all the lower parts of v^^j^/^ : For fo far as the 
Nile o'refiows, is perfed foil. A fample whereof I hope 
youftill retain 5 and let me entreat you to be veryexait 
in weighing it this year, that you may be fure whether 
it be heavier in the time of the Inundation fas is gene- 
rally believ'd) than before or after: And when, and in 
what proportion, it encreafos. 
The Boundaries . of this overflow ("whidi are never lo 
miles from the Channel, that I faw, generally fcarce ^of 
it, and in fome places but a mile or two, (the Delta ftill 
excepted which is univerfally covered, all but the North 
fide to the Sea, and a little to the Eaft for fome miles a- 
bove 
