It is largely by sheer accident that enough prints and plates have survived for us to see "Photographing the Frontier -- Part Two" at the Smithsonian Institution.

The glass plate photographic negatives of those pioneer days were fragile, bulky and heavy. Often they were the first things discarded in the trash after a photographer's death if they somehow had survived hazards of fire, flood and breakage. The photographs in the Smithsonian exhibition come from plates or, more likely, original prints preserved by heirs, museums, libraries -- and luck.

The show opened Wednesday at the Museum of History and Technology and will continue for several months.

And even though cumbersome equipment ruled out snapshot spontaneity in these early photographs, there still is a simple appealing candor often missing from the self-conscious photography of later years. That is one reason why these photographs of frontier America are such valuable historical documents.

They record the lifestyles of the pioneer days from post-Civil War to the early 1900s. There are families before their crude log cabins, saloons, muddy main streets, a women's millinery shop showing that hard-working pioneer wives still enjoyed bright finery in headgear, the gallows hanging of an Indian, gamblers, children playing a schoolyard, a Fourth of July parade.

Frontier photographers had to be brave and persistent. C. R. Savage, who traveled in a wagon designed to hold his bulky camera equipment, complained about the hardships and hazards. The wagon train wasn't going to stop for Savage to take his pictures, and Savage sometimes found himself alone, several miles behind the wagon train, and prey for roaming Indians searching for stragglers.

Savage's problems explain why wagon train trips are almost undocumented by photographers.

The names of most of the early photographers have been obliterated along with a great deal of their work. But the surviving prints and plates give a glimpse of western pioneer life.

The show is being circulated by the Smithsonian Traveling Exhibition Service.