JDH writes re. meteorological observations. He reminds Wheatstone that he left England in Nov on HMS 'Sidon' with Lord Dalhousie & arrived in Egypt in Dec. He explains the observations he made on the effect of the sun on the soil temperature at Cairo & results he got in different locations at different times of day, including at the Great Pyramid. On board the Honourable East India Company Steam Frigate "Moozuffer" from Suez to Calcutta [Kolkata] JDH took temperature & dew point readings but his barometer was disturbed by the engine. He includes a table of his observations. He observed that the waters in the gulf are saltier than any other sea & the salinity decreases towards Mocha before normalising. This variation is unlike anything JDH observed on the voyage with Captain Ross. The Persian Gulf is said to have similar salinity to the Indian Ocean. JDH discusses the winds & currents in the Red Sea. Winds are particularly strong in the Gulf of Akabar & were violent up to Jibbel Teer. He mentions the depression of the Red Sea below the level of the Mediterranean, two occurrences of a crepuscular arch witnessed between Madras [Chennai] & Calcutta & the beautiful sunsets at Aden. JDH is now travelling with Mr Williams up the banks of the River Soane to Mirzapore, having reached the Dunwar Pass from Burdwan & climbed the highest mountain in lower Bengal: Paris-Nath [Parasnath or Shikharji]. He is taking observations regularly to determine the effect of climate on vegetation over large areas. Next he will go to Sikkim in the east Himalaya. He carries his Newman's Portable barometer everywhere personally. He explains how he observes terrestrial & solar radiation. JDH describes an aurora he observed on 14 Feb [1848], it was the more impressive than any he has seen in Scotland or the South Polar regions & included an auroral arch. He has sent the account to be published in Calcutta & also invites Wheatstone to share it with The Philosophical Club & The Athenaeum.