When William Mitchell wrote this diary he was suffering from the diabetes that led to his death. At the time diabetes was little understood and the only treatment was through diet. During the 19th century however chemical tests were developed to measure the amount of sugar in the urine and kits for this purpose were available. William Mitchell seems to have had such a kit. The testing involved heating a small amount of urine in a test tube, observing the colour and the sediment, and measuring its specific gravity. One adjusted one's diet according to the results.

In this diary William Mitchell recorded the results of his daily urine tests, the amount of urine he had passed in twenty-four hours, and the food he had eaten at each meal. For convenience he recorded the meals in shorthand, some of it in English letters - probably mostly the initial of the food item - and some of it in symbols.

Where William got these symbols from is not known, but they appear to be from one of the numerous shorthand systems in use in the 19th century. It is difficult to find examples of many of these systems and, as each new one borrowed from previous systems, many of them are similar. Some of the symbols William used are found in one system while others are not. His symbols for "the" and "that", for example, have the same meanings in Samuel Taylor's system, but other symbols he used do not occur in Taylor. Bibles, prayer books and sermons were often produced in shorthand and it is possible that William had one of these. He must have had at least some sort of list of symbols.

In any case William Mitchell does not seem to have been fluent in writing shorthand, as he did not spell whole words in it, but simply took a set of symbols and assigned his own meanings to them. He had done this in the earlier diaries, and listed their meanings on page 36 of the first diary and again on the last page of diary 3 (18790926 -18800122). Some of these same symbols, with some new ones, he used in this diary also, but with different meanings. Travelling around looking for farming land, William found it useful to have symbols for words like "selection", "horse", "creek" and "road", but recording his diet needed a whole new vocabulary, and the same list of symbols had to be used. Unfortunately William did not list their meanings in this diary, so even if one found a shorthand system containing all these symbols one would still have to guess the meanings he assigned to them.

Nevertheless, without knowing the exact meaning of each symbol or letter, it is still possible to make same sense of the diary. It is obvious that one dot stands for breakfast, two dots (:) for dinner (lunch) and three for tea. The SP or S followed by figures and the references to "cooking brown" and "sugar" are connected with the urine test, and the figure in pints is the quantity of urine passed. Careful study of the text allows some reasonable guesses to be made about the foods. (A list of foods recommended and not recommended appears on page 88, but it is not clear at what stage William was given this or how strictly he followed it.)

As well as monitoring his diet William was seeking other remedies for his illness. Among the jottings on page 23 he has apparently copied a prescription, starting with the Rx symbol, ending with the dosage, and including codeia (= codeine), extract of nux vomica, belladonna and possibly birch-bark (betula = birch). On page 27 another jotting mentions "uva ursi" and "buchu". Uva ursi, or bearberry, and buchu are shrubs whose leaves are used in herbal medicine, particularly for urinary problems.

William was also putting his trust in Warner's Cures: the Safe Cure, a general cure-all; the Safe Pills, and the Diabetic Cure. American H. H. Warner made his first fortune as a manufacturer of fire- and burglar-proof safes and later used the word "safe" in his patent medicines. His remedies were very popular and there were factories in several countries, including one in Melbourne. The medicine bottles are now prized collectors' items. It is possible that Warner's also provided urine analysis, as William mentions on page 52 that he "sent water to Warner" and on page 49 that the number of his case in Warner's register was 1291.

In the end none of these things helped William Mitchell very much and he died a few months after this diary ends.