The diaries show that a new crop, potatoes, first planted in Norðoyri in 1823, gradually displaced grain and had almost taken over by 1855. This happened because of potatoes' weather resistance, stability and more flexible harvesting period compared to grain. Furthermore, the journals contain information or proxy data that admits statements on climatic variation. When e.g. transforming the data on potatoes and barley yields into 10 years moving averages, both crops show similar chronological yield variations, with good harvests in the early 1830s, early 1860s and mid-1880s, separated by poorer periods with minima around 1825, 1844 and the 1870s. The analysis of the journals also shows that haymaking for winter fodder for cows was relatively stable.