1. Source enquiry skills; cross referencing Aims To understand that the reliability of a source can be checked by comparing it to another source To weigh up the differences and similarities between tow sources on order to reach a judgement on reliability.

2. Cross referencing This helps the historian to check the accuracy of the sources. By looking at points of similarity and difference you can reach a judgement about the sources reliability.

3. Cross referencing When you cross reference sources you need to follow certain steps: Have a clear idea of what it is you want to check in the first source (list the details you are checking) Check the second source to see what it says about each of these details. Are they confirmed, challenged or just mentioned? What attitude is shown in the first source? Is it positive or negative? Does it stress any particular aspect? Check the attitude of the second source. Is it similar or different? Look at the differences between the sources. Are they small differences, for example in numbers, or big differences that might even contradict each other? Weigh up the importance of the similarities and differences between the two sources.

4. Cross referencing and reliability By cross referencing sources you can check the reliability of sources. This requires you to look for points of similarity and difference in the sources provided.

5. Practice time Source A: Lister’s description of using carbolic acid in a letter to his father in 1866. ‘Though I hardly expected any success I tried carbolic acid on the wound to prevent the formation of pus in the leg. Well it is now eight days since the accident and the patient has reacted just as if there had been no open wound.’ Source B: Many surgeons soon lost their enthusiasm for Lister’s carbolic acid method when they discovered that keeping the wards clean using ordinary disinfectants was just as effective at stopping infection. Furthermore, Lister refused to changed his methods. Even in1883, one of Lister’s assistants described Lister as wearing an ‘old coat, stiff and shining with dried blood’ when he carried out his operations.

6. Possible questions Both these sources deal with Lister’s discovery of carbolic acid as a method to reduce infection during operations. Your own knowledge should tell you that the use of carbolic acid significantly reduced death rates. However, there was significant opposition to the use of the acid. Make sure you know what this was. Two possible questions using these sources: 1.Study sources A and B. How far can we rely on these sources to assess the success of Lister’s carbolic acid in the late 19 th century? Refer to the sources and use your own knowledge. (9 marks) 2.Study sources A and B. Which of these sources gives the most reliable account of how quickly Lister’s ideas were adopted by the medical profession? Explain your answer using the sources and your own knowledge. (9 marks)

7. Summary It is very rare to find a source that totally agrees with another, so you need to make a judgement about how far the second source backs up the first one, based on what you have found in the process of cross referencing. This includes a careful matching of the detail but should also take into account other issues of reliability as well.