Some readers may have wondered how Galileo got along, while Professor of Mathematics at Pisa, on the small salary which he received. He tells us that he gave public lectures on his own account; he gave private tuition, and he kept as many as twenty students as boarders, looking after the housekeeping himself. It is interesting to note that the late Lord Kelvin's father, Professor Thomson, had to resort to public lectures on his own account when he became Professor of Mathematics in Glasgow University. The reason for the small salary in this case was that the retired professor had the first claim on the salary, and there was not much left for the new professor. But we shall hear something of Professor Thomson when we come to consider the life of his distinguished son, Lord Kelvin.

In Galileo we find the same ingenious mechanical ability as in Lord Kelvin; both employed workmen to manufacture and sell instruments which they had invented.

We have remarked already that part of Galileo's financial difficulties was due to the payment of dowries promised to his two sisters' husbands. His brother was also a burden upon him; not only did he fail to pay his share of the dowries, but he required assistance for himself and his family. Then Galileo had to provide money to place his two daughters in a convent. One of these girls, whose religious name was Sister Maria Celeste, was a great favourite with the father. That the father and daughter were very much devoted to one another is abundantly clear from the correspondence preserved by Galileo.

Maria Celeste was always wondering in what way she might be of any assistance to her "very illustrious and most beloved lord and father," as she so often styled him. We hear very little of the other sister, who seems to have been wanting in the devotion of Maria Celeste, who was a great comfort to her father. Galileo preserved all her letters, and although his letters to her were probably destroyed at the convent upon her death there, we can see from Maria Celeste's replies that her father's letters were very much prized by her. On one occasion she writes, "I put by carefully the letters you write me daily, and when not engaged with my duties I read them over and over again. This is the greatest pleasure I have."

Sister Maria Celeste was so very grateful to her father for every attention paid to her that one is inclined to think she had in mind the fact that she had no legal claim upon her father. Her mother had lived with Galileo without any marriage ties, and when she married another, evidently with Galileo's good-will, she left the two daughters and the one son with the father. But Maria Celeste was a very real daughter to her father; her distress at his misfortunes is most pathetic. When news came that Galileo was free to leave Rome Maria Celeste wrote: "I wish I could describe the rejoicing of the Mother and Sisters. On hearing the news Mother Abbess and many of the nuns ran to me, embracing me and weeping for joy and tenderness."

Galileo was known personally to those in the convent through his visits to his daughter. They even asked him on one occasion to mend their convent clock (a primitive timekeeper) and to help them in other ways.

Galileo's son Vincenzio was often a great worry, as well as a cause of considerable expense. The selfishness of the son is in sorry contrast to the daughter's devotion. But one is pleased to find that Vincenzio was attentive to his father in his old age. It was Vincenzio who drew the flan of a pendulum clock according to his aged father's dictation. But before the idea could be carried out Galileo died, and strange to say, the son did not make any use of the idea till seven years later. Unfortunately, while he was engaged in this first attempt to construct a pendulum clock he, too, fell ill and died. It was some five or six years later that the distinguished Dutch scientist Huygens constructed the first clock controlled by the regular to-and-fro swing of a pendulum.

These few incidents give us a glimpse of Galileo's private life. We cannot wonder that at times he became despondent under the treatment he received at the hands of the Inquisition. While he was not subjected to physical torture, we find him suffering under the great restraint put upon him. On one occasion we find him cursing the time he has devoted to these labours, and regretting having given so much of his results to the world. "I feel even the desire to destroy for ever, to commit to the flames, what remains in my hands. Thus I should satisfy the burning hate of my enemies. These thoughts aggravate my numerous physical sufferings, and cause me persistent insomnia."

It is of interest to note what great personages were living in our own country while Galileo was playing his important part in Italy. We saw in the preceding chapter that while Galileo was a schoolboy in Italy, Queen Elizabeth and Mary Queen of Scots were reigning here. But they had both passed away before Galileo's troubles began, for at the time he invented the telescope James VI of Scotland had become James I of England. Even he had died before Galileo was in serious trouble with the Inquisition, so that Charles I was King of England at the time of Galileo's death.

Among the great personages who lived here during Galileo's lifetime were Shakespeare, and, of course, Lord Francis Bacon. Also the famous Dr. William Gilbert, who was the first to make a serious study of those phenomena which are classified under the title of Electricity and Magnetism. It is interesting to find that Galileo, in his dialogues, gives great praise to Gilbert, for we know that Bacon, on the other hand, sought to belittle Gilbert's great work.

Our world-famous poet John Milton visited Galileo in his captivity in Italy. This was long before Milton became blind; he was then a young man of twenty-nine years. Galileo by that time was totally blind, and had reached more than the allotted span, being about seventy-five years of age. When Milton addressed the Lords and Commons against the proposed licensing of printed books, he made mention of his visit to Galileo in his captivity.

It is interesting to note that in the year in which Galileo died the great English scientist Sir Isaac Newton was born.

Galileo's great mind was active to the very last, despite his constant sufferings. Some of his enemies sought to prevent Galileo's friends burying the philosopher's body in consecrated ground, but this permission was granted, on the understanding that the great public funeral, which had been arranged, should be abandoned. The Pope requested also that the proposed public monument should be cancelled. But modern Italy has done much to amend matters. In 1841 an exquisite temple of Galileo was opened; the cost of this monument is said to have been forty thousand pounds. Since then the Scientific World has done public homage to his name on three occasions. First on the three-hundredth anniversary of his birth, then on the three-hundredth anniversary of his first lecture in Padua, and more recently on the tercentenary of the invention of his telescope. All these great international commemorations should help us to realise how very much we owe to this great Hero of Science.