THERE are six million frozen moments stored in a secure compound behind the scenes of the largest public reference library in Europe. Each one holds a distilled human emotion, from the joys of sporting victory to the horrors of war; from the promise of New Towns to the disappointment of closed shipyards. The locations stretch from the banks of the Clyde to the surface of the moon.

The Herald picture archive is a national treasure, the family album of the millions of people who have lived, worked and holidayed in Scotland, along with the equivalent of postcards from their relatives around the world. It reflects almost a century of newspaper photography, countless moments in time captured for ever, to remind us how we used to live, who we looked up to, where we travelled and what we enjoyed in our limited leisure time.

As a journalist and a historian, I was doubly delighted to be shown round the archive, have the sections and subsections pointed out, and be left to browse the hundreds of metres of clean white shelves, smooth brown files and slick, shiny sheets of paper with images from around the world and around the country, the visual memory of one of the great metropolitan daily newspapers. The collected work of hundreds of thousands of people who were both technically proficient and artistically gifted.

But where to start? To cut through my sense of being overwhelmed - the same emotion felt by small boys in sweetshops - I chose three packets linked only by alphabetical sequence: Fraud, Freaks and Freemasonry. I had to start somewhere, I reasoned. The first revealed images of smudged £5 notes, the second a parade of unnecessarily tall women, rubber-faced men, feral children and Mongolian contortionists. The content of the third file is a secret. Actually, it contained photo after photo of Masonic street parades, the most interesting showing a torchlit procession in Melrose, with faces grim and shining in the light of the blazing batons, like a Ku Klux Klan rally.

My Uncle Bert was a Master Mason, I remembered, and my professional mask dropped. What if I could find my family's history here, not just the collective memory of the Scots? This was a personal, and quickly emotional, quest for my identity, rather than the biography of a people and a nation. Pick a packet from the shelf, any packet, and the personal associations are there. Maryhill Primary School, then Allan Glen's and the University of Strathclyde, all there in their brown folders, all looking just as I remember them. The streets I lived in, north, south, east and now west of the city.

Family holidays in Millport and Rothesay, faithfully recorded in The Herald archive, two-dimensional representations of three-dimensional days, the images - and the edges - dulled by time, just like my own memories. Sadness, too, looking at the file called "Prisoners (British Prisoners in Germany) from the Hitler War", hoping against all logic and likelihood for a glimpse of my father as a prisoner of war in Stalag IVG. Gunner William Seth Scott was not to be found, but at least he made it home, unlike the hundreds of thousands of people disposed of in mass graves, photographed and given a strange afterlife in this corner of the Mitchell Library. I could not bear to look into a neighbouring file, Horror Pictures: Scenes from Concentration Camps.

In the Glasgow files, I saw streets I have walked down, ferries, buses and trains I have travelled in, hospitals and houses I've visited, places I have thought about, written about, even photographed. I found Lochgelly, where my father's father was raised, and Fairlie, where my mother's parents met and where my great-aunt Ella sang in the church choir. There was a handful of folders for various Rons, Ronnies and R D Scotts, but none for me. I had to look, but there is plenty of me in many of these pictures: my childhood, education and working life in the city, and my connections across Scotland. All of us can say the same, for this is our family album, preserved for generations.

Lost places, forgotten places, abandoned places; they are all in the archive, waiting to be called upon as witnesses to the past in newspapers, exhibitions, books and TV programmes, and - perhaps most importantly - to be bought by readers and passed around, talked about and reminisced over, becoming part of a family's past and, of course, its present and future.

The Herald archive is the collective memory of our community, informing our identity, nourishing our roots and reconnecting us to the ever-present past. And photographs, like love letters, go straight to the heart. The personal is there; the political and the spectacular, too. The assassination of John F Kennedy, the Lockerbie and Piper Alpha disasters, major and minor wars, the rise and fall of industrial society, football successes, murder and mayhem, weddings and beddings, births and deaths. All human life, as another newspaper used to promise, is here.

Dr Irene O'Brien, senior archivist at the Mitchell Library, responsible for Glasgow City Archives, and chair of the Scottish Council on Archives, knows the value of repositories. "Archives have a key role to play in the cultural life of the people of Scotland," she says. "They provide the bedrock for our understanding of the past, showing us - and future generations - how we come to be what we are as a nation, a community or an individual. And, as more and more of us are reaching out to trace the history of our families and their communities, we are using archives to make that direct connection with our family members and the places they lived and worked.

"Photographic archives are one of the most vital tools in allowing us to make those connections with our past. They provide a visual record of the people, places and events that helped shape our history. The Herald picture archive is a vital part of the nation's archival heritage."

Her views are echoed by Dr Tom Normand, lecturer in the history of art and photography at the University of St Andrews and the author of Scottish Photography: a History. He says: "This kind of archive is fundamental to our sense of history and identity. When I was selecting photographs for my book I became conscious that there was a host of images that were excluded from the visual culture. The greatest part of these were photographs taken for newspapers. In a sense these have been viewed as throwaway; only valuable in respect of the story they were accompanying. But this isn't the case.

"Apart from the fact that photo-journalists and newspaper photographers have produced some of the most searing images of the modern period, the newspaper photograph offers one of the most acute and revealing insights into the state of the nation. The Herald picture archive is one of the richest, most diverse and most relevant we have available; it's also a fine collection of extraordinary images."

The archive is an unusually broad repository. Academic and national collections may hold a narrow, formal view of people and events, but newspapers print illustrations from every corner of human experience.

Ray McKenzie, who lectures at Glasgow School of Art and is a founding member of the Scottish Society for the History of Photo- graphy, champions the immense cultural value of picture archives. "Photographic archives have become so indispensable in the study of history that achieving any kind of realistic understanding of our past would be almost unthinkable without making use of them, especially those amassed by newspapers," he says. "Newspaper reportage may well be the first draft of history', but it is the photographs that bring it fully and truly to life."

  • To find out about photographs available from the archive, call 0141 302 7360 or visit www.thepicturedesk.co.uk