It shall be the duty of the state treasurer to annex to the annual estimates of the appropriation required for the public service of the year, which may have been made by former acts, and also a statement of the sums remaining in the treasury from the appropriations of former years, estimating the amount of those sums which will not be required to defray expenses incurred in a previous year, and showing the whole amount which will be subject to the disposition of the government in the year to which the estimates apply.