This series of manuscript notebooks contain Babbage’s rough sketches, notes and ideas relating to the Difference and Analytical Engines. They demonstrate his thought processes and development of the functions and design of his machines. Interspersed among the sketches is a quantity of descriptive material. Some of this describes in general terms the working of apparatus or arithmetical algorithms. A small amount describes the overall function of the Analytical Engine.

Some of the contents are difficult to interpret since they include many sketches of ideas that were not incorporated in drawings or notations. According to Bromley, only a portion of the ideas were ever adopted and further developed. The notebooks include other subjects, such as the notion of a machine to play noughts and crosses or personal matters, such as complaints about the amount of time lost due to noisy street musicians.

Babbage described his notebooks as 'Scribbling Books' in the Notations, Drawings, etc. up to 26 Oct. 1837 after which he called them ‘Sketch Books’.

The first series consists of 16 notebooks that contain 'The first rough notations of the Difference and of the Analytical Engines, developed by sketches and calculations in Nine Volumes. Some of these became the basis of the drawings...'. The other notebooks in this sequence 'contained materials belonging to the same subject. The dates are various and irregular'. The second series contains the 'four more volumes of a later date' as described by H.P. Babbage in his book 'Babbage's Calculating Engines' published in 1889. The third series consists of additional notebooks that do not form part of the original series. The fourth series comprises a set of miscellaneous papers bound in three volumes. In some cases, for example in notebook S3, Babbage started separate sections, each with its own pagination from the back of the volume, written with the volume itself inverted.

The series also includes 25 loose sheets (mostly scraps of paper) relating to the notebooks (1837-1843). These sheets comprise draft notes and sketches of the content of the scribbling books on both front and back of the papers. They also include notes indicating into which notebook the draft information had been copied. The loose notes do not appear to be in any particular order and have been numbered in the order in which they were found. Of interest is one of the sheets on which Babbage noted the five principles of algebra.

The notebooks relating to the design of Difference Engine No. 1 were passed by Babbage to the government in 1842. They are now lost.