The authors have observed tracks which they believe to be due to mesons in photographic plates placed near a target bombarded by 380 Mev alpha particles. For a 10-minute exposure in the cyclotron, about 50 meson tracks are found along the 3-inch edge of a photographic plate. The mass has been determined by measuring the bending in the magnetic field and the range in emulsion. From the first 50 meson tracks measured they find a mass of 313 {+-} 16 electron masses. It is highly probable that these mesons are the heavy mesons described by Lattes, Occhialini, and Powell.

Article chronicles the establishment of the Grand River Hydro-Electric Company and how the organization built dams to stop flooding of the Grand River.

Notes and Documents section for Volume 26, Number 2, Summer 1948. It includes an explanation for the bibliography of George E. Foster, a report on manuscripts acquired by the society regarding Catholic Indian Missions, letters written by the "Lost Captain" of Fort Gibson, a note on a constitutional amendment regarding the direct vote for senators, and the minutes for the annual meeting of the Oklahoma Historical Society held on May 26, 1948.

Article chronicles the establishment of the first medical society within Indian Territory using correspondents with the founding members and meeting minutes.

Article provides a list of post offices established within the Indian Territory as they appeared on official documents while explaining their significance.

Article chronicles how the Robe family established missionaries throughout the Indian Territory and their impact on the region.

Article chronicles the life of George Allen Henshaw, a delegate for the state of Oklahoma' constitutional convention.

Article chronicles the life and career of Byron Norrell, an editor for multiple newspapers published in the Oklahoma and Indian Territories.

Article details the life and customs of early settlers within the region then known as No Man's Land, a place without a constitutional government. Currently, the region is known as the Oklahoma Panhandle.

Article chronicles how the Presbyterian Church established the Tullahasse Mission within the Creek Nation and the mission's achievements in the region.

Article narrates the history of Day county in Oklahoma as it evolved through the cattle industry through the experiences of the author.

Article recounts the author's experiences settling within Oklahoma Territory after the Land Run of 1889.

Article recounts the development of junior colleges within the state of Oklahoma.

Article chronicles the establishment and dissolution of the Otoe and Missouria Reservation, the sixth and last reservation established in the Cherokee county.

Article honors Robert Lee Williams: a leading figure in the movement to make Oklahoma an official state in the United States, a delegate for the constitutional convention, and a justice on the state's Supreme Court.

Article reports on Reverend R. M. Loughridge's experiences visiting Creek county as a missionary during Oklahoma's pioneering days.

Article chronicles the establishment of the 389 treaties made between the United States and Indigenous tribes that made tribes people wards of the federal government.

Article recounts why the Northern Cheyenne tribe fled Oklahoma to Montana during the late 1800s. These events cumulated into the Dull Knife Raid.

Notes and Documents section for Volume 26, Number 1, Spring 1948. It includes an announcement of the distribution of an Index, a note on the presentation of the portrait of Dr. Angelo C. Scott, a note on the burning of the oldest building in Oklahoma, a note on the retrieval of records from the Five Civilized Tribes Agency, an announcement regarding old Greer county records, a list of recent accessions to the society's library, and the minutes for the quarterly meeting of the Board of Directors of the Oklahoma Historical Society held on January 29, 1948.

Notes and Documents section for Volume 26, Number 3, Autumn 1948. It includes an announcement of the appointment of Dr. Emma Estill-Harbor to the position of president of the Oklahoma Historical Society, letters written by President Franklin D. Roosevelt, a recount of Jeremiah Curtin's experiences within Indian Territory, a summary of the meeting of the Tulsa County Bar Association, a note on a gift received from the British House of Commons, a note on a Confederate memorial, a list of members of the Oklahoma Press Association and of the OHS who recently passed, and an announcement of the cancelation of the society's quarterly meeting.

Article honors the men from Oklahoma who have died fighting in World War II after the last publication of a similar list. The country would continue to be a major player in the war until 1945.