After Melzi’s death in 1570, his heirs started to spread his material. They didn’t understand how valuable the manuscripts were, reason why they initially kept them in an attic and then sold them to friends and collectors for a very low price. The person who had a lot to do with the mix up of the manuscripts was Pompeo Leoni. He wanted to divide the artistic drawings from the technological ones by ripping and moving the pages and he did that by sectioning the original manuscripts. He finally created two big collections: the Atlanticus codex (or Atlantic codex) and the Windsor collection, which has approximately 600 drawings. With the same method, Leoni composed at least 4 other booklets. From 1637 to 1796, part of the manuscripts was kept in the Ambrosian library from which they were smuggled by Napoleon when he arrived in Milan. In 1851, part of them were brought back to Milan; some stayed in Paris, some others in Spain where some will be found only in 1966. That’s the reason behind the big scattering of Leonardo’s writings, that today are divided in 10 different codes:

It can be found at the British Library in London. Arundel codex is a collection bound in Moroccan leather and it contains 283 sheets of paper of various sizes; the papers that were originally part of the collections were then glued to papers of support (28×18 cm). In this collection various subjects are taken into consideration: studies of physics and mechanics, of optics and Euclidean geometry, studies of weight and architecture; the latter include the works for the royal residence of Francesco I in Romorantin (France). Most of the pages can be dated to around 1478 and 1518.

Stored in Milan at the Ambrosian Library, the Atlantic codex contains drawings, which for the most part can be dated around 1478 and 1518. In this codex are taken into consideration different topics: studies of mathematics, geometry, astronomy, botany, zoology, military art. Today it is reorganized in 12 volumes bound in leather and formed by 1119 support papers of 65×44 cm, containing papers of various sizes. The name of this collection comes from the fact that at first the papers were all part of a very big volume (the volume of atlas).

It is preserved at the Trivulziana library of the Sforzesco castle in Milan and it is formed by a booklet made of 55 papers (20.5×14 cm) instead of the original 62. It contains not only studies of military and religious architecture, but also Leonardo’s self-taught studies that helped him to improve his literary knowledge. Most of the pages can be dated around 1487 and 1490.

This Codex is held at the Royal Library of Turin and it comprises 17 pages (instead of 18) and measures 21×15 cm and it can be dated around 1505. It mainly deals with the flight behaviour of birds that Leonardo analysed with a meticulous mechanical approach, and just like that he also studied the purpose of the wing, the air resistance, winds and air currents.

The work consists of two volumes: 2037 ex-code B (?) and 2038 ex-code A. They are preserved at the Institut de France, in Paris. The work consists of two manuscripts (sizes 24×19 cm) and they are cardboard bound. They were originally part of the manuscript A from which they were torn by Guglielmo Libri in the mid 19th century. They contain studies of painting (Ash. 2038) and other studies (Ash. 2037) that Leonardo did probably between 1498 and 1492.

They’re held at the France institute of Paris and they consist of 12 manuscripts. Some of them are parchment bound, others are leather bound and some are cardboard bound. They all have various sizes: the smallest one is Codex M (10×7 cm), the biggest one is Codex C (31.5×22 cm). Conventionally, they are given a letter of the alphabet, from A to M, for a total of 964 paper sheets. Various subjects are taken into consideration in these manuscripts: military art, optics, geometry, the flight of birds, hydraulics. Most of the pages can be dated around 1492 and 1516.

It consists of 3 parchment-bound manuscripts called Forster I (14.5×10 cm), Forster II (9.5×7 cm) and Forster III (9×6 cm). They’re held at the Victoria and Albert Museum of London. They contain studies of geometry, weights and hydraulic machines, developed by Leonardo approximately between 1493 and 1505.

It is a leather- bound manuscript and consists of 36 paper sheets with dimensions of 29x22cm and contains not only studies of hydraulics and water motions (1504-1506) but also studies of astronomy. It was purchased by Bill Gates in 1994.

They’re held at the Windsor Castle (Royal Collection) and consist of around 600 drawings of different sizes and they aren’t bound. They contain studies of anatomy and geography, horses studies, drawings, caricatures and also geographic maps. They belong to different periods of Leonardo’s life, between 1478 and 1518 ca.

They’re her at the National Library of Madrid, where they were discovered only in 1966. They are two manuscripts bound in Moroccan Red. In order to be identified faster, they are called Madrid I and Madrid II. Most of the pages of Codex Madrid I, dating around 1490 and 1496, consists of 192 paper sheets (21×15 cm) of studies of mechanics. Whereas Madrid II consists of 175 paper sheets (21×15 cm) and focuses on studies of geometry and it can be dated around 1503 and 1505.

Source: Leonardo da Vinci science and technology national Museum