into a circle of four feet diameter. These, for duration, can only be exceeded by your iron wheels. Pray, have you completed that ingenious invention?

What is become of honest Mr. Ketilby? Does he go on with his printing schemes, or has he got into some better employment?

They tell us here, that some person with you has discovered a new moving power, that may be of use in mechanical operations; that it consists in the explosion of iron tears chilled suddenly from the melting state in cold water. That explosion I have often seen in drops of glass with wonder, understanding it no more than they did in the time of Hudibras, who makes a simile of it, which I repeat because it is probably so long since you read it.

"Honor is like that glassy bubble,

That gives philosophers so much trouble;
Whose least part cracked, the whole does fly,
And wits are cracked to find out why."

May I ask you, if you know any thing of the application of this power, of which I have not at present the smallest conception?

I have completed my stove, in which the smoke of the coal is all turned into flame, and operates as fuel in heating the room. I have used it all this winter, and find it answer even beyond my expectations. I purpose to print a little description of its use and construction, and shall send you a copy.

I hope Billy and Jenny continue, and always will continue, as happy as when I knew them. My best wishes attend them, being as ever, with sincere esteem,

Dear Sir,

Your most obedient humble servant,

B. FRANKLIN.

TO M. DUBOURG.*

Concerning Dr. Stark.t

4 May, 1773.

The young physician whom I mentioned is dead, and all the notes which he had left of his curious experiments are by some accident lost between our friends. Sir John Pringle and Dr. Huck (Saunders); but these gentlemen, if the papers cannot be recovered, it is to be presumed, will repeat the experiments themselves. B. FRANKLIN.

However glad I was of the occasion, I forbore indulging myself in the pleasure of congratulating by the first post, my dear double confrère, on his election into our Royal Society, because Mr. Walsh undertook to give you the information, which would make a second expense unnecessary, and I saw I should soon have this opportunity by the favor of M. Poissonnière. I rejoice in the event, as you seemed anxiously concerned about it, and as we have done ourselves honor in distinguishing and associating a merit so universally known and acknowledged.

I am pleased to hear that you are engaged in the

Translated from M. Dubourg's edition of Franklin's Works, Vol. II. p. 312.- EDItor.

The works of Dr. Stark, including the experiments alluded to, have since been published.

consideration of hospitals. I wish any observations of mine could be of use to you, they should be at your service. But it is a subject I am very little acquainted with. I can only say, that, if a free and copious respiration is of use in diseases, that seems, from the experiments I mentioned to M. Dubourg, to be best obtained by light covering and fresh air continually changing; the moisture on the skin, when the body is warmly covered, being a deception, and the effect, not of greater transpiration, but of the saturation of the air included under and in the bedclothes, which therefore can absorb no more, and so leaves it on the surface of the body. From these experiments I am convinced of what I indeed before suspected, that the opinion of perspiration being checked by cold is an error, as well as that of rheum being occasioned by cold. But as this is heresy here, and perhaps may be so with you, I only whisper it and expect you will keep my secret. Our physicians have began to discover that fresh air is good for people in the small-pox, and other fevers. I hope in time they will find out, that it does no harm to people in health.

We have nothing new here in the philosophic way. I shall like to hear how M. Lavoisier's doctrine supports itself, as I suppose it will be controverted.

With the greatest esteem, I am ever, Dear Sir
Yours most affectionately,

B. FRANKLIN

P. S. Enclosed I send you some pamphlets relative to our American affairs for your amusement. Sir John Pringle bids me present his compliments. He interested himself much in the election.

TO M. DUBOURG.

Inquiries on the Causes of Taking Cold.

DEAR FRIEND,

London 29 June, 1773.

I have not time now to write what I intend upon the cause of colds, or rheums; and my opinions on that head are so singular here, that I am almost afraid to hazard them abroad. In the mean time, be so kind as to tell me at your leisure whether in France you have a general belief, that moist air, and cold air, and damp shirts or sheets, and wet floors, and beds that have not been lately used, and clothes that have not been lately worn, and going out of a warm room into the air, and leaving off a long-worn waistcoat, and wearing leaky shoes, and sitting near an open door or window, or in a coach with both glasses down, are all or any of them capable of giving the distemper we call a cold, and you a rheum, or catarrh? Or are these merely English ideas?

I am ever, with the greatest esteem and respect,
Dear Sir, yours, &c.

B. FRANKLIN.

Preparatory Notes and Hints for writing a Paper concerning what is called Catching Cold.

Definition of a Cold.

It is a siziness and thickness of the blood, whereby the smaller vessels are obstructed, and the perspirable matter retained, which being retained offends both by its quantity and quality; by quantity, as it outfills the vessels, and by its quality, as part of it is acrid, and being retained, produces coughs and sneezing by irri

tation.

How this Siziness is produced.

1. By being long exposed in a cold air, without exercise; cold thickens glue.

2. By a diminished perspiration, either first from breathing and living in moist air, or, second, from the clogging of the pores by clammy sweat dried on and fastening down the scales of the skin; or, thirdly, by cold constringing the pores partially or totally, sleeping or waking; or, fourthly, by having eat food of too gross particles for free perspiration, as oysters, pork, ducks, &c. People are found frequently costive after much bathing.

3. By repletion, as when more is thrown into the habit by eating and drinking than common perspiration is capable of discharging in due time; whence the vessels are distended beyond their spring, and the quantity of contained fluid, that should be briskly moved to preserve or acquire a due thinness, is too weighty for their force, whence a slow motion, thence viscidity. This repletion is increased by a constipation of the belly happening at the same time. In an approaching cold, more water is made than usual.

4. By cooling suddenly in the air after exercise. Exercise quickening the circulation, produces more perspirable matter in a given time, than is produced in rest. And though more is likewise usually discharged during exercise, yet on sudden quitting of exercise, and standing in the air, the circulation and production of perspirable matter still continuing some time, the over quantity is retained. It is safer not to go into water too cold.

5. By particular effluvia in the air, from some unknown cause. General colds throughout a country. By being in a coach close, or small room with a person having a cold.