During his second Karakoram expedition in 1925 Mr. Ph. C. Visser collected some 70 rock specimens from the valley of the Hunza and its tributaries. The following is a petrographic description of these specimens and I gladly take this opportunity of thanking Mr. Visser for entrusting me with his valuable material. Geologists are much endebted to this energetic explorer for bringing together such a considerable number of samples under circumstances in which all carriage had to be reduced to a minimum and when so many other calls were being made on his time and energy. A collection made by a layman and therefore taken without many observations on mode of occurrence, must naturally be of limited value. When, however, it concerns a region that is almost terra incognita from a geological as well as from a geographical point of view, it may serve to give us an insight into the more salient features, especially petrographic and to some extent structural as well, and therefore constitute an important contribution to geological knowledge. Geologists will all hope that Mr. Visser will soon be in a position to add to the collections he has already made.