353	LAW AND FREEDOM  IN HISTORY
inspiration, and ethos—must be notably longer than the Time-interval
between the Parthenon and the Olympieum, considering that the Olym-
pieum is manifestly a mere variation on the Parthenon's architectural
theme. In reality, as we happen to know, beyond dispute, the Time-
interval between the Parthenon and the Olympieum, so far from being
notably shorter than the Time-interval between the Olympieum and the
Ayfa Sophia, was half as long again, and an estimate of the relative
length of the intervals, based on the hypothesis of invariability in the
tempo of change, would be utterly misleading.
If we turn our attention from ecclesiastical to naval architecture and
apply the hypothesis of invariability in the tempo of change to the dating
of successive types of battleship in the history of the British Navy, we
shall find ourselves inveigled into inferring that the Sovereign of the Seas
(launched in a.d. 1637) must have been separated from the Queen
(launched in a.d. I839)1 by a notably shorter Time-interval than that
separating the Queen from the Royal Sovereign (launched in a.d. 1891).
On this a priori method of reckoning, no other conclusion would be
plausible, considering that the Queen was a wooden three-masted square-
rigged sailing ship with her guns mounted along her broadsides, whose
points of difference from the Sovereign of the Seas were merely points of
detail, whereas the Royal Sovereign, with her gun-turrets fore and aft
and her iron hull, steel armour, pair of funnels, and propellers driven
by steam, was a Martian sea-monster that would not have been recog-
nized as being a ship, in any intelligible sense of the word, by any sailor
in Codrington's squadron at Navarino on the 2oth October, 1827.
"We should be similarly misled if we were to put our trust in the same
a priori principle in trying to estimate the relative Time-intervals be-
tween the equipment of a Roman soldier in the last days of the Roman
Empire in the West, a Saxon soldier in the comitatus of the Holy Roman
Emperor Otto I, and a Norman knight depicted on the Bayeux tapestry.
Considering that the round shields and the gladiator's square-rimmed
crested helmets with which Otto's soldiers are equipped are manifest
variations on the equipment of Majorian's soldiers,2 whereas William
the Conqueror's soldiers are equipped with Sarmatian conical helmets
1 'As late as 1845 there was laid down at Devonport a Sanspareil designed upon the
lines of the ship of the same name captured from the French in 1794, although, it is
true, the vessel was never actually launched as a sailing line-of-battle ship, but, while
—--••- 	   '	"	•   •-	••     •" ^guns, and launched
t (London 1901,
7 the line to be
Navy Records Society, in a letter of the 2 3rd January, 1951, in which he kindly gave
this information to the Librarian of the R.I.I.A. in answer to an inquiry made on the
present writer's behalf).
z No doubt we have to allow for the possibility that the portrayal of a tenth-century
'Western soldier's equipment may have been influenced by a perhaps unconscious con-
servatism that may have made it look more like a fifth-century Roman soldier's equip-
ment than it actually was; but such conservatism cannot have gone so far as to blind
"Western artists in the Dark Ages to the visual evidence, for they did not ignore the new-
fangled equipment of an eleventh-century knight: on the contrary, they evidently took
a delight in reproducing it faithfully to the facts. On this showing it seems reasonable to
assurtie, that- their protrayal of a tenth-century Western soldier's equipment is likewise
essentially true to life.