The Batak territories were completely white spots on the maps in 1840. Contemporary maps contained only skylines of the mountains who are to see when passing along Sumatra's west coast on a ship. It wasn't safe, for the Bataks are resistant people, living deep in mountainous forests. They always kept themselves in isolation. Junghuhn's orders were manyfold. He had to map the region, explore the climate and the fertility of the soil, explore usable natural sources, particularly wood for ship building. About the Bataks he was wanted to find out as much as possible, their political attitude, language and alphabet, customs and, of particular interest, their notorious cannibalism.
The Batak Village Gudarim Baru. Image from Junghuhn's publication "Die Battaländer auf Sumatra" (1847).
Franz Junghuhn landed in October 1840 together with his scientific assistent Hermann von Rosenberg in the bay of Tapanuli on an island hosting a Dutch fortress. That's near where is nowadays the town of Sibolga.
Soon after they started the expedition into densly forestred Sumatra, Hermann von Rosenberg got lost in the jungle while hunting. Junghuhn could find and rescue him, but Rosenberg suffered a severe fever and had to be brought back to the next bigger Dutch settlement.
Junghuhn, nevertheless, continued alone exploring the southern Batak countries. Penetration and surveying the land brought him to the borders of his physical and also mental abilities. The local Batak were some years before havoced by martial Malays and were very suspicious about strangers. By the way, Bataks always were very suspicious about strangers, including Bataks from other tribes. Eventually it became impossible to continue further northwards, towards Lake Toba and the Batak Karo mountains. In the 18 month he spent on Sumatra, Junghuhn was ten month sick, lying in his basic camp south of the volcano Lubu Radja. He suffered dysentery and the inflammations of some of the countless bites of leeches.
In his own words:
In Tobah the locals denied me to survey the land with the argument, it would serve the purpose of the erection of a fortress. In Hurung I could only observe the surroundings when hiding in bushes, for similar reasons. In Silingdong my work got forbidden for it were pure magic. I was urged to pack my things and leave the area.
Additionally there are the mountains with all the steep slopes. It's only possible to move on foot. In one day one has to cross 30 to 40 streams, some of them very cold, others are warm or even hot. Crossing a stream or river means to put all the equipment above the head, because the water somtimes rises almost up to the shoulders. In daytime one is plagued by masses of small leeches who come by 20 or 30 and creep under the clothes and bite anywhere on the body; they even bite through socks and trousers. The bites cause painful furuncles. In nighttime therefore are always mosquitoes around.
Most of all one has to mind safety, to load at least six rifles and keep rotational guarding awake with the servants to scare the locals away."
JUNGHUHN, 1847, translation by Asienreisender
Not to speak about the weather. I personally experienced on several journeys the heaviest rainfalls in Batak countries on north Sumatra. It's pouring an immense amount of big raindrops, mostly starting in the afternoon. Then it's raining for at least some hours, sometimes throughout the whole night. It get's really dark; there must be huge clouds queuing in the Batak mountains, coming from the Indian Ocean. Next morning it's usually sunny again.
As more surprising is what Junghuhn obtained in the eight month he was half the way healty and could act. Despite all the suspicion he could find out much about all the aspects of culture and all-day-life of the Bataks. Above all he managed very well to survey and map the southern Batak territories in detail with the sophisticated techniques of his time. He showed an enormous strength of will to accomplish the mission. Not even the much more developed island of Java was mapped that well in the time as the southern Batak territories by Junghuhn.
A Batak hamlet on Samosir Island, Lake Toba. It's still very traditional with the exception of the tin roofs and the electrification. Batak hamlets are surrounded by an earth wall on which dense bushes or trees grow; here it is bamboo. It's so hidden, that a hiker does not easily see it, and there is only one entrance. Image: Asienreisender, 2009
His maps were the basic tool for all the Christian missionaries who came in the following decades into these areas to convert the Bataks to Christianity (including local celebrity Ludwig Ingwer Nommensen). Some of them ended up as food for the cannibals. Junghuhn, on his part, was personally against the conversion of local people to the Christian religion, as he made clear in his book "Licht- und Schattenbilder aus dem Innern Javas".
The maps also include the first mapping of Lake Toba, although only after descriptions of Batak people, because it wasn't possible for Junghuhn to reach Lake Toba on his expedition.
Fifty years later, around 1890, the Dutch colonial power subdued the whole Batak countries in the 'Batak Wars'.