The Balearic Islands  are an archipelago of islands in Spain in the western Mediterranean Sea, near the eastern coast of the Iberian Peninsula. The four largest islands are Mallorca, Menorca, Ibiza, and Formentera. Many minor islands and islets are close to the larger islands, including Cabrera, Dragonera, and S'Espalmador. 

The Quaker City dropped anchor in the Gulf of Cagliari, some two miles from the town, at 9:00 p.m. on 13 (not 12) October. Captain Duncan wrote, “An official informed us that cholera existed at Cagliara and that foul bills of health were issued to every vessel leaving— We had heard enough and hastily leaving returned to the ship” (Charles C. Duncan 1867, entry for 13 Oct).

August 10, 1867, Sam and companions visited the Island of Capri by chartered steamer. Mark Twain Project: Quaker City Itinerary

The Flinders Island, the largest island in the Furneaux Group, is a 1,367-square-kilometre (528 sq mi) island located in the Bass Strait, northeast of Tasmania, Australia. Flinders Island is situated 54 kilometres (34 mi) from Cape Portland and it is located on 40° south, a place known as the Roaring Forties.

The Sandwich Island:  

Twain sailed from San Francisco aboard the Ajax on March 7, 1866, arriving in Honolulu 11 days later.

He went to the island of Maui April 14, 1866 ands studied sugar plantations.

Returned to Oahu May 22, 1866 for four days and attended the legislature.

Sam and companions spend two days on the island of Ischia while the Quaker City remained in quarantine at Naples, from August 7 to August 9, 1867. Mark Twain Project: Quaker City Itinerary

Hawaiʻi  is the largest island in the United States, located in the state of Hawaii. It is the southeasternmost of the Hawaiian Islands, a chain of volcanic islands in the North Pacific Ocean. With an area of 4,028 square miles (10,430 km2), it has 63% of the Hawaiian archipelago's combined landmass. However, it has only 13% of Hawaiʻi's population.

The island of Maui is the second-largest of the Hawaiian Islands at 727.2 square miles (1,883 km2) and is the 17th largest island in the United States. Maui is part of the State of Hawaii and is the largest of Maui County's four islands, which include Molokaʻi, Lānaʻi, and unpopulated Kahoʻolawe.

Oahu  also known as "The Gathering Place", is the third-largest of the Hawaiian Islands. It is home to roughly one million people—about two-thirds of the population of the U.S. state of Hawaii. The island is within Honolulu County and the state capital, Honolulu, is on Oahu's southeast coast.

Wikipedia

At Sea, July 2.

Dr Folks—

Although the British built Fort Mackinac to protect their settlement from attack by French-Canadians and native tribes, the fort was never attacked during the American Revolutionary War. The entire Straits area was officially acquired by the United States through the Treaty of Paris in 1783. However, much of the British forces did not leave the Great Lakes area until after 1794, when Jay's Treaty established U.S.

The Quaker City was scheduled to stop at Malta but reports of cholera prevented that and the ship bypassed the island.

Clemens reached Port Louis April 15, 1896 and went ashore the next morning.  They took a train to the resort town of Curepipe and stayed there for nearly two weeks.  They sailed via Mozambique for South Africa April 28th aboard the Arundel Castle.

Due to its southerly location and the moderating effect of Lake Erie, it has a slightly milder climate than inland areas. Its climate is one of the mildest in Canada, and the island has long been used for vineyards and wine making. The wine industry was started here in 1860 and died out in the early twentieth century, but was restarted in the 1980s. The island is an agricultural based community which grows about 2,000 hectares (5,000 acres) of soybeans, about 400 hectares (1,000 acres) of wheat, 200 hectares (500 acres) of grapes, and a few hectares of specialty corn.

The excursion program specified a stop of a “day or two” at St. Michael (São Miguel), the largest of the Azores, which was somewhat farther east than Fayal (Charles C. Duncan 1867 [bib10640]). But, as Clemens explained in his first letter to the New York Tribune,

The Quaker City made port at Cagliari October 13, 1867 but because of cholera no one left the ship.  The ship then proceeded to Algiers.