Simplify the following text for a Grade 9 native English-speaking person.
Original: His custom-made `` linnaeus-thermometer '' , for use in his greenhouses , was made by Daniel EkstrÃ m , Sweden 's leading maker of scientific instruments at the time and whose workshop was located in the basement of the Stockholm observatory .
Simplified: His custom-made â linnaeus-thermometer , â for use in his greenhouses , was made by Daniel EkstrÃ m , Swedenâ s leading maker of scientific instruments at the time . EckstÃ m 's workshop was located in the basement of the Stockholm observatory .