Have a B&W tiff file from 1901 glass slide, when I scanned it went blured, how to fix?

I have some glass slides which are negatives from photographs taken in 1900 to 1902. When I scanned them the resulting files are TIFF file but they seem darker and out of focus.

I have copied and converted them to JPG and edit it that way but the results are poor.

Can I edit a tiff file to restore the image to the quality on the glass slide?

If so how?

regards

Michael - Sydney Australia