Your journal would not afford me sufficient space for an _excursus_ to establish the suggestion, _not_ assertion, that I have adventured as to the _domestic_ use of the Alphabetic and Degree Psalms, but there is negative evidence that these Psalms were _not_ used in the Jewish liturgy. I will only refer you to Lightfoot's ninth volume (Pitman's edition), where the Psalms used, and indeed the whole service of the Jews, is as clearly set forth as the Greek service is in the liturgies of Basil and Chrysostom. T. J. BUCKTON. Lichfield. [Footnote 4: "Eadem ratio, ab honestate ducta, eandem pepererat apud Romanos legem. Gellius ex Fabio Pictore, _Noct. Attic._, lib. x. c. 15., de flamine Diali: Scalas, nisi quæ Græcæ adpellantur, eas adscendere ei plus tribus gradibus religiosum est. Servius ad _Æneid_, iv. 646. Apud veteres, Flaminicam plus tribus gradibus, nisi Græcas scalas, scandere non licebat, ne ulla pars pedum ejus, crurumve subter conspiceretur; eoque nec pluribus gradibus, sed tribus ut adscensu duplices nisus non paterentur adtolli vestem, aut nudari crura; nam ideo et scalæ Græcæ dicuntur, quia ita fabricantur ut omni ex parte compagine tabularum clausæ sint, ne adspectum ad corporis aliquam partem admittant."--Rosenmüller on Exod. x. 26. The ascent to the altar, fifteen feet high, was by a gangway, [Hebrew: KBSH].] * * * * * THE SCREW PROPELLER. (Vol. ix., p. 394.) ANON. is clearly mistaken in thinking that, when Darwin says that "the _undulating_ motion of the tail of fishes might be applied behind a boat with greater effect than common oars," he had any idea of a screw propeller. He meant not a _rotatory_, but, as he says, an "undulating" motion, like that of the fish's tail: such as we see every day employed by the boys in all our rivers and harbours, called _sculling_--that is, driving a boat forward by the rapid lateral right and left impulsion of a single oar, worked from the stern of the boat. It was the application of steam to some such machinery as this that Darwin seems to have meant; and not to the special action of a _revolving cut-water screw_.