Through the span of a century, men have arisen now and again who, by their ability, their dint of application and inspiration, have sifted facts of science amidst a maze of confusing evidence, and who have thus left an indelible impression upon the sands of time. Such men have not merely unveiled scientific truths, not only contributed their iota to the sum total of scientific knowledge, but have also added dignity and luster to the science they have pursued. Birbal Sahni was one among such men. To his brother Dr. M. R. Sahni, and one who learnt the first principles of Science from him when scarcely of school-going age, his passing away has meant a break, a snapped link with the memories of a cherished past. If this fraternal tribute goes beyond the pale of ordinary biographical sketches, it is to share wish his numerous friends certain aspects of his life which even those who were most intimately associated with him could scarcely know of.

    Birbal Sahni was the third child of his parents, the late Professor Ruchi Ram Sahni and Shrimati Ishwar Devi. He was born on the 14th of November, 1891, at Bhera, a small town in the Shahpur District, now a part of the West Punjab, and once a flourishing center of trade, which had the distinction of an invasion by the iconoclast, Mahmud of Ghazni. The immediate interest that centers round Bhera is enhanced by the fact that this little town is situated not far form the Salt Range which may be described as veritable "Museum of Geology". Excursions to these barren ranges, where lie unmasked some of the most interesting episodes and landmarks of Indian geology, were often co-ordinated with visits to Bhera during his childhood, particularly to Khewra. Here occur certain plant bearing formations concerning the geological age of which Birbal Sahni made important contributions in later years.
Although Bhera become his ancestral home, his parents were at one time settled much farther afield, in fact at the riverine port of Dehra Ismail Khan on the Indus, and later migrated to Lahore.
    It is learnt from his autobiography that father, still at school, was obliged to leave Dehra Islamil Khan owing to reverses of fortune and the death of his grandfather who was a leading citizen of the town. With the change of fortune, life became different and difficult. Undeterred, his father walked with a bundle of books on his back all the way from Dehra Islmail Khan to Jhang, a distance of over 150 miles, to join school. Later at Bhera and at Lahore, he distinguished himself as a scholar. He educated himself entirely on scholarships that he won. He was thus brought up in a hard school of life, and was entirely a self-made man. His father was a person of liberal views, and during his career he became one of the leaders of the Brahmo Samaj movement in the Punjab, a progressive religious and social upsurge which had then freshly taken root. Undoubtedly his father imbibed these ideas during his sojourn in Calcutta in his early days. He gave practical effect to his views by breaking away completely from caste. And when the call came, father, then a man of advanced years, stood knee-deep in the sacred mud of the tank of the Golden Temple and removed basket loads of it upon his frail shoulders to assist in clearing the accumulated silt. His religion knew no boundaries. Always patriot, he threw himself heart and soul into the struggle of independence and even tasted the severity of the bureaucratic baton at the Guru ka Bagh. He fought valiantly for the rights of his country men, and was more than once on the verge of arrest.
    About 1922, when he returned the insignia of the title conferred upon him by the then government, he was threatened with the termination of his pension, but his only answer was that he had thought out and foreseen all possible consequences of his action. He retained his pension!
    It was inevitable that these events left their impression upon the family and were also imbibed by the family members. Therefore, if Birbal Sahni became a staunch supporter of the Congress movement, it was due in no small measure to father's living example. To this may be added the inspiration he derived, even if on rare occasions, form the presence of political figures like Motilal Nehru, Gokhale, Srinivasa Shastri, Sarojini Naidu, Madan Mohan Malaviya and others who were guests at their Lahore house, situated near the Bradlaugh Hall which was then the hub of political activity in the Punjab.
    His mother was a pious lady of more conservative views, whose one aim in life was to see that the children received the best possible education. Hers was a brave sacrifice, and together they managed to send five sons to British and European universities. Nor was the education of the daughters neglected in spite of opposition form orthodox relations, and her elder sister was one of the first women to graduate from the Punjab University.