Some years since greenhouses were to be heated by the waste heat from limekilns. It was a good idea, but it does not seem to have made much headway. Probably those who would like to save the heat do not care to go into the lime-selling business, while those who now make the lime and lose the heat know nothing of the greenhouse management. There surely ought to be something in the idea if the horticultural and lime-burning intellect could be evolved from our brain.

Heating by a limekiln.

Heating by a limekiln.

As some attention is being again given to the subject, through some of the Philadelphia papers recommending the heating of the Exhibition Buildings by this plan, we reproduce an illustration we once gave of the plan, as it has in a measure been forgotton.

It will be seen that the figures a, 6, c, simply indicate the arrangement of an ordinary limekiln, while the other letters indicate the portions of a saddle boiler with its flow and return pipes over the top of the kiln.

Although this twenty-acre building could probably be heated in this manner, it might not perhaps be very agreeable to the frequenters of the beautiful Fairmount Park to have a " nasty lime market" with its main depot within its boundaries. However, it is for us to show what may be done, - for others to entertain the practicability or desirability of applying it.