In spring 1907 and 1908 the authors of this note participated in a geological excursion along the northern coast of Lake Ladoga. The excursion began with an examination of the Imatra waterfall and the surrounding rocks with characteristic signs of the Ice Age. From Imatra we drove to the city of Serdobol and from here we set off on foot along the shore of Lake Ladoga, getting acquainted along the way with the rocks of this area and with two ore deposits, Velimeki and Pitkaranta, which was the final destination of our trip. Without having in mind a description of all the material, for our brief note we selected only rock samples that we took along the way from the town of Serdobol to the Velimeki iron mine inclusive, the most interesting from a petrographic point of view.
This note examines the expression of the length of the arcs of an ellipse and a hyperbola using infinite series (see article). Adding all these equalities and making reductions, we obtain the following formula, which is nothing more than the Wallis formula. The same result could be obtained by finding the arc length of the hyperbola.
