ster manuscript, I must for now limit myself to referring the reader to the Atlantic Codex for this comparison since copying those lists in full, as would be opportune, and commenting on them with respect to the Leicester Codex would force me to make a practically unending digression and note. If this proves possible, it will be done at leisure. Other lists, also of significant interest with regard to the Treatise on water and the Leicester manuscript, may be found in the Arundel Codex (cf. sheets 35 r. and v., 45 r., 122 r., in Richter, op. cit., II, § 925-928) and in ms. F (sheets 23 v., 24 r., 24 v.). since the development of the ideas appears to have reached the same stage, embracing, in large part, the same issues, and because the individual titles of the chapters or books correspond more often than not with the topics mentioned or dealt with in the Leicester Codex; and because, lastly, in some cases the subjects are grouped together in the same way. These coincidences appear so strange as to suspect that one might have to look for them in the frequent references found in descending numerical order (35 M, 29 M, 25 M, 23 M, 22 M, 23 m, 23 m, 21 m, 21 m, 20 m, etc., as far as 1° m (sheet 74 r. -a and 74 v. -a; to sheet 79 r. -a, 17m is found only once) throughout the said list of the Atlantico Codex, as so many references to the pages of the Leicester manuscript, of which it would have provided a sort of index. But, beginning to make a comparison from an analytical point of view, especially as regards the arrangement of the subjects in the manuscript with respect to the order of the references offered by the cited list of the Atlantico Codex, no elements can be found to confirm such doubt; so much so as to think that the list itself is only a little anterior or preparatory to, That this list was not intended for use as an index but as the preparation for another work is shown by the words “E qui si dirà: se l’acqua infra l’acqua non pesa” [And here it shall be said: if water inside water has no weight], etc., which Leonardo writes after one of the listed topics (“Come contro al natural moto delle cose gravi l’acqua surge a l’altissime sommità de’ monti, partendosi da l’infime profondità del mare” [On how against the natural motion of heavy things water springs to the highest peaks of the mountains, from the deepest depths of the sea.] Atlantic Codex, sheet 74 r.-a). And the proposition which Leonardo therein demonstrates, of maintaining that parallelism between the motion of water in the veins of the earth and that of blood in animals, proves that the date of the list of the Atlantic Codex cannot be later than 1508. or parallel Cf. sheet 74 v.-b the figure and the word: “Pescaia d’Ognisanti” [Ognisanti Weir]; which call to mind the margin drawings of the Leicester manuscript. to the Leicester manuscript, to which it may have served to a large extent, helping to reassemble from other places ( and perhaps, mainly from a notebook indicated as M) Cf. the references, already mentioned (see above no. 3, pg. 13), to “book A”. the topics of the Treatise. The analogies are too many and too evident, especially those provided by the very varied themes which follow on from one another on sheet 74 r. -a of the Atlantico Codex, for them not to be related to the Leicester manuscript; and this relation, at least for sheet 74 r. -a, points in favour of the list in the Atlantico Codex being earlier, in which the arrangement of the subject appears less advanced than in this Codex. The considerations already made would seem to exclude that the Leicester manuscript could have been started prior to 1503. From that year, up to about halfway through 1508, lies the range of most probable hypotheses regarding the period when the manuscript was compiled. From the beginning of March 1503 Cf. Atlantic Codex, 77 r.-b; and see Uzielli, Ricerche, etc., cit., (1st ed.) Florence, Pellas, 1872, pg. 164. to the 30 May 1506, Leonardo continued his studies of hydraulics in Florence, alternating them with studies of flight Cf. Atlantic Codex, sheet cit. above, and see the two dates of April 1505 on sheet 18 v. (salvaged) of the Codex on the flight of birds (published by Piumati, Paris, Rouveyre, 1893; and the K manuscript, from sheet 3 r. to 14 r. , with work on the Battle of Anghiari, with studies of solid geometry Cf. the Forster codex and the date of beginning it, 12 July 1505 shown on sheet 1 r. Some mention of solid geometry is also to be found in the K manuscript, on sheets 52 v. and 53 r. and other mathematical occupations. During this period the following note is believed to have been written in the manuscript K, belonging in part to the Florentine stay terminating in 1506 One may recognise without hesitation on sheet 14 v. of the K manuscript, in the comparison of the antique reproductions remaining of the Lotta per lo Stendardo (Fight for the Standard, the knight on the right (with the fluttering cloak), whose face, shown in profile, with his mouth open to shout, was based on one of the sketches in the Pest gallery. and in part to the time in Milan immediately following it Cf. ms. K, sheets 93 v., 99 v., 109 r.-108 v., 109 v. : “la gocciola che chade in locho d'equal densità e planjtia risalterà cholli stremj del suo vesstigio for della sua circhunferentia con equal disstantia e così de converso”. (a drop falling in a place which has the same density and is on a flat level will bounce back with the same force and to the same extent as it has penetrated below this point and vice versa) ms. K, sheet 56 r. Other notes in pencil in the same codex may be provisional notes intended for use in the book on water. see the vague note: “la luna densa e gra densa e grave” [The moon is very dense and heavy], on sheet 1 r. of the K manuscript and cf. the Leicester manuscript, sheet 2 r.; see too the description: “de incremento Nili opera d’Aristotile piccola” on sheet 52 v. of the K manuscript, noting the importance which Leonardo gives to the information regarding the Nile in the Leicester manuscript.