[Quint. I. vii. 7.] Quaeri solet, in scribendo praepositiones, sonum
quem junctae efficiunt an quem separatae, observare conveniat: ut cum
dico _obtinuit_, secundam enim B litteram ratio poscit, aures magis
audiunt P.

This change, however, is both so slight and so natural that attention
need scarcely be called to it. Indeed if quantity is properly observed,
one can hardly go wrong. If, for instance, you attempt, in saying
_obtinuit_, to give its normal sound to B, you can scarcely avoid making
a false quantity (the first syllable too long), while if you observe the
quantity (first syllable short) your B will change itself to P.

C appears to have but one sound, the hard, as in _sceptic_:

[Mar. vict. Keil, v. VI. p. 32.] C etiam et ... G sono proximae, oris
molimine nisuque dissentiunt. Nam C reducta introrsum lingua hinc atque
hinc molares urgens haerentem intra os sonum vocis excludit: G vim
prioris pari linguae habitu palato suggerens lenius reddit.

Not only do we find no hint in the grammarians of any sound akin to the
soft C in English, as in _sceptre_, but they all speak of C and K and Q
as identical, or substantially so, in sound; and Quintilian expressly
states that the sound of C is always the same. Speaking of K as
superfluous, he says:

[Quint, I. vii. io.] Nam K quidem in nullis verbis utendum puto, nisi
quae significat, etiam ut sola ponatur. Hoc eo non omisi, quod quidam
earn quotiens A sequatur necessariam credunt, cum sit C littera, quae ad
omnes vocales vim suam perferat.